Key to My Heart Love/Proposal Cake

Introduction: Key to My Heart Love/Proposal Cake

Here is one of my newest cake designs, complete with simple instructions. The cake is a strawberry, cream cheese heart cake. You can use this cake to propose to your loved one or simply tell them you love them! I really couldn’t have done this project without my sister Grace (check out her Instructables graciepickle). Now, without further adieu lets make this cake!


Please during this entire project be creative! Remember, keep your surface clean the whole time you are making this cake, use an anti-bacterial cleaner.


  • 1 Cup Unsalted Butter
  • 2 Cups Sugar
  • 1 Teaspoon Vanilla
  • 4 Eggs
  • 1 Cup Whole Milk
  • 2 1/2 Cups Flour
  • 1/2 Teaspoon Salt
  • 2 1/2 Teaspoons Baking Powder

Strawberry Jelly

  • 4 cups frozen strawberries (you can use different frozen fruit if you want)
  • 1/4 cup water for the strawberries
  • 1/3 cup sugar
  • 2 tsp lemon juice
  • 1 tbsp powdered gelatin
  • 1/4 cup cold water for the gelatin

Italian Meringue Butter Cream

  • 1/2 cup + 6 tbsp Granulated Sugar
  • 4 large egg whites
  • 1 cups unsalted butter soften
  • 1/2 teaspoon vanilla extract

Cream Cheese Mousse

  • 1/2 cup whipping cream
  • 1/2 cup chopped white chocolate or white chocolate chips
  • 4 ounces cream cheese
  • 1-3 tablespoons powdered sugar divided
  • 1/2 teaspoon vanilla extract
  • pinch of salt

Mirror Glaze

  • 10 oz Granulated Sugar
  • 7 oz Sweetened Condensed Milk
  • 5 oz Water
  • 4 tsp Gelatin Powder
  • 2.5 oz Water
  • 7 oz White Chocolate
  • Gel coloring

Lock, Key, and Compartment

  • Fondant
  • Gel food coloring


  • Oven/Stove
  • Fridge/Freezer
  • 8-inch cake pans
  • Large pan
  • Tall glass
  • Fondant tools
  • Stand Mixer
  • Hand Mixer
  • Parchment paper
  • Tooth Pick
  • Scissors and Knives
  • Cake plate
  • Sause pans
  • Candy thermometers
  • Spoons and Forks
  • Measuring Cups and spoons
  • Bowls
  • A laminated piece of paper (explanation to come)
  • A lighter or culinary torch

Step 1: The Cake

This is Yolanda's "Ultimate Vanilla Cake" (instructions and ingredients from her website, How To Cake It).

  1. Preheat the oven to 350°F. Line three 8-inch cake pans with parchment ( you will only need two of the cakes)
  2. Sift the flour, baking powder, and salt into a medium bowl and whisk together
  3. With a hand mixer ( you can use a stand mixer) beat the butter, sugar, and vanilla on medium speed until light and fluffy
  4. Add the eggs two at a time and mix until incorporated
  5. Add the flour mix in four parts and the milk in three parts alternating in between each addition Don't over mix!
  6. Pour the batter into the pans and bake for about 40 minutes, when done check with a skewer, when it comes out clean it's done
  7. Wait for it to cool and its ready

Step 2: Strawberry Jelly

This jelly is very tasty and has good texture. If you want you could swap the frozen strawberries with other frozen fruit like raspberries or mangos.

  1. Sprinkle gelatin over 1/4 cup cold water. Set it aside for 5-10 minutes
  2. In a saucepan, combine strawberries, sugar, water and lemon juice. Bring to a simmer, and cook for 5-10 minutes, continue to stir
  3. Put it in a blender and blend until smooth, then strain through a sieve until smooth
  4. Heat the gelatin in the microwave until it melts. Add to the strawberry mixture
  5. Pour the Jelly into one 8-inch pan with parchment paper (In the picture I split it into two pans but you only need one)
  6. Freeze or refrigerate (I recommend freeze)
  7. To get the jelly out lift up the parchment paper, if you want you can dip the pan in hot water

Step 3: Italian Meringue Buttercream

I'm using Yo's famous Italian Meringue Buttercream! (It's very tasty and smooth). I cut her recipe in half but if you want extra frosting the original quantities are on her website.

  1. In a small saucepan, combine the sugar and 1/2 cup water. Place over medium heat and bring to a boil. Clip a candy thermometer to the side of the pan
  2. While the sugar syrup is heating, put the egg whites in the bowl of a stand mixer fitted with the whisk attachment. When the syrup reaches 230°F on the candy thermometer, begin to whip the egg whites on medium/high speed. Whip until the egg whites are stiff
  3. When the syrup reaches 240°F, immediately remove the pan from the heat and, with the mixer running, pour the syrup into the egg whites in a very thin stream. Pour the syrup between the side of the bowl and the whisk attachment
  4. Whip the meringue at high speed until thick and glossy and the bowl is no longer warm on the outside, about 8 to 12 minutes
  5. With the mixer running, add the butter, a piece at a time, whipping until each piece is fully incorporated before adding the next. Scrape down the sides of the bowl with a spatula occasionally. After all the butter has been added, continue to whip the buttercream until it’s thick and smooth, 3 to 5 minutes. Beat in the vanilla and the food coloring

Step 4: Cream Cheese Mousse

This mousse is sooooooooooooooo delicious and very easy to make! I find that the cream cheese flavor goes very well with the strawberries. If cream cheese is not your thing or perhaps you want a different flavor (chocolate would be very good) then you can easily swap this recipe out with one to your liking.

  1. Beat the whipping cream at high speed until stiff peaks form
  2. Gently melt the white chocolate in 30-second increments, stirring frequently, in the microwave
  3. Beat the cream cheese and 1 tablespoon of powdered sugar until light and fluffy (It's okay to use the same beaters)
  4. Beat in the white chocolate, vanilla extract and salt on medium speed until well combined
  5. Fold in the whipped cream. If it's not combining easily, you can use the mixer to beat it in on the very lowest setting, just until combined, don't overmix

Step 5: Fondant Lock and Key

The lock and key are pretty simple to make but not necessary if you just want a heart cake that's okay too.

  1. Cut a square of gold fondant. (dyed with brown, yellow and orange gel food coloring)
  2. Cut out a keyhole shape with whatever you desire. It's basically a circle and trapezoid
  3. Add details with fondant, like circles, a hammered metal texture, or lines
  4. Cut out two small squares of fondant. Wrap them around a straw and seal the edges. Wait for them to harden a little, then attach them to the lock using a small strip of fondant (you can texture the strip so it looks like welded metal)
  5. To make the key roll out a snake of fondant and cut a slit in the key
  6. Cut out two or three prongs and add to the slit
  7. Roll out another snake and form it to a ring (don't attach both sides0
  8. Put the rest of the key in the ring and bond together
  9. Wait for the key and lock to dry overnight ( or bake on the lowest setting of your oven for 10 minutes and wait for it to cool)
  10. Mix together some gold dust and almond extract
  11. Paint the gold onto the key and lock
  12. Make a fondant glue by micing water and fondant
  13. Add three rods to the hinge with the glue, wait to dry again or bake, then re dust

Step 6: Assemble Cake

Now for the fun part! Assembly of the cake! Please look at the pictures to clear up any confusion.

  1. Level the cakes
  2. Put a hefty dollop of buttercream on one cake
  3. Level out the frosting, put the strawberry jelly on top, followed up with another cake
  4. Crumb coat the whole cake
  5. Cut around the edges with scissors or a knife to smooth out the edges
  6. Cut a V in the top of the cake (look at the pictures to clear up the instructions)
  7. Score a line on top of the cake from the base of the V along the whole cake (Line #1)
  8. Score two lines from the end of the first line to the side of the cake (Lines #2 and #3)
  9. Cut out lines #2 and #3
  10. Attach the cut-out pieces to the opposite sides of the cake to form a heart (a very rough heart) I had to cut the main cake to make the edge straight
  11. Frost the whole cake
  12. Smooth the whole cake with the laminated paper disinfect the paper!
  13. Put the mousse on the cake and smooth
  14. Put the cake in the freezer
  15. Finish smoothing out the cake by dipping your very clean fingers in hot water then smoothing out the bumps
  16. Measure the lock and draw a square of a smaller on some parchment cut out the parchment and place on the cake
  17. Cut out the square
  18. Line the cavity with frosting
  19. Measure out five fondant squares and attach them to the frosting cavity
  20. Put back in the freezer

Step 7: Mirror Glaze

This is the part that makes the cake glossy and gives it a nice finish. Personally I like the glaze, it tastes nice and feels nice, but the glaze texture is not for some people. I recommend testing it first to see if you like it, if you do, great! If not, the cake will look very nice with a second coat of buttercream.

Make the cavity cover

  1. Cut out a square of parchment paper and attach with toothpicks

Make the glaze the recipe I'm using is from Sugar Geek Show

  1. Add the sugar and first quantity of water to a medium-sized saucepan and heat over medium-low heat, stirring occasionally
  2. Pour the second quantity of water into the powdered gelatin and mix it with a spoon. Leave to fully absorb for 5-10 minutes
  3. Combine white chocolate and sweetened condensed milk in a large saucepan
  4. When the sugar and water mixture begins to simmer, remove from the heat and add the gelatin. Stir until the gelatin has dissolved, it's okay if there are some lumps, but not too many
  5. Put the white chocolate in the mixture and leave to sit for 5 minutes to melt.
  6. Use a whisk to stir the glaze until the chocolate has completely melted.
  7. Add the gel food coloring and stir until well-mixed. Pass the glaze through a fine strainer to remove any lumps. Leave the glaze to cool.
  8. Put the cake on a tall glass in a large pan to collect the drips
  9. Once the glaze has cooled to 90º F / 37º C, pour it over the frozen cake carefully, try not to get too much glaze on the parchment cavity
  10. Let cool, if you want you can re-warm the glaze for a second coat
  11. Once the cake is coated to your liking remove the drips with a hot knife
  12. Transfer the cake to a serving plate
  13. Remove the parchment on the cake and spoon some glaze onto the left-over white part and bond together with the torch
  14. Leave to cool
  15. Add candies and some notes or an engagement ring!
  16. Place the lock

Step 8: The Done Cake

Your cake is done! Now you can insert your key and open up the lock to the heart of your significant other!

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    2 years ago

    Well, isn't this beautiful! Awesome glaze :)