Usually I make this cake in a cake of 12" (30cm) diameter. This is quite an unusual size for a cake tin, and you are most welcome to used the same recipe to make a smaller cake, but you might want to scale down the recipe accordingly. You don't have to scale down if you'd like a thicker cake base.
Step 1: Gather your ingredients
8oz self-raising flour
8oz caster sugar
4 large eggs
1 teaspoon baking powder
1 teaspoon vanilla essence (optional)
2 packets orange jelly (I used Hartley's jelly tablets which came in 135g packs)
100g dark chocolate (I use a high quality 70% variety, but could be replaced with milk chocolate if desired)
A 12" diameter baking tin
A really big mixing bowl
A shallow, wide bowl
A small bowl
Food processor OR Electric whisk OR a wooden spoon and lots of elbow grease
Step 2: Prepare the jelly
Once you've got the hot liquid jelly, pour it into the large shallow bowl and put it in the fridge. The reason this step comes first will become apparent when you try to pour unset jelly over a hot cake as I once did (it crawled off like some kind of swamp monster).
Step 3: Prepare the cake
2. Grease and line your cake tin - it's easiest to put the cake tin on top of the paper, draw a circle round the base in pencil and then cut it out, then place that in the bottom of the tin. Use the paper that the butter comes in to grease the sides of the tin.
3. Using your food processor or electric whisk or wooden spoon, cream together the butter and sugar until pale and fluffy. You will see no remaining lumps of butter in the mixture, and it should turn into a ball.
4. Add the eggs to the mixture, beating well to combine. If you're using vanilla essence, add it to the mix at this point.
5. If necessary, sift together the baking powder and flour before adding them to the mixture. Stir to thoroughly combine.
6. Pour the cake mix into the prepared tin. Bake in the preheated oven at 180ºC for about 30 minutes until risen, golden brown, and springy to the touch.
7. Leave the cake to cool in the tin for 5 minutes, then transfer to a wire rack. When completely cool, transfer to a serving plate.
Step 4: Combine cake and smashing orangey bit
Loosen the jelly from the bowl using a knife, flexible spatula, or any implement that won't damage the jelly too much. Then invert the bowl over the centre of the cake. The jelly will probably be somewhat reluctant, but with a few taps on the bottom of the bowl it should come out. Et voila! A smashing orangey bit!
Step 5: Cover the cake with chocolate
Alternatively, melt the chocolate in a bain marie (a bowl set over a pan of simmering water) if you don't have a microwave.
Leave to cool for a few minutes, or you may inadvertently melt the jelly when pouring it over the top. Start at the centre of the jelly, letting the chocolate run off and smoothing it over the sides of the cake using a palette knife.
Leave the cake until the chocolate is set.