My daughter had a brilliant idea of making a Minecraft creeper mosaic chocolate bar out of white and black chocolate, though for reasons for space we just made the head.

Consumables:

Dark chocolate bar
White chocolate bar
Wax paper

This works best with chocolate bars that are divided into squares, like the Ghirardelli's ones that we used.

Tools:

Microwave
Knife
Cutting board
Flat bottom microwave safe dish/plate

Step 1: Mosaic Pieces

If you score a chocolate square with a knife--even a butter knife--you can break it into quarters. You can then cut the quarters into rectangles as needed.

My daughter made the pieces as she went on rather than all in advance.

Step 2: Layout

Put wax paper on microwave safe flat-bottom dish/plate.

Lay design out on wax paper. Keep the pieces as close together as possible.

Step 3: Microwave

Microwave the design until the chocolate is just melted. This took a little over a minute in our microwave.

If you do this right, the chocolate will look perfectly solid but be actually melted. If it looks melted, you're coming a little too close to going too far. I suggest running the microwave for about 45 seconds, and then every fifteen seconds probing gently with a knife to see if it's melted.

Step 4: Welding the Squares

Put a piece of wax paper on top of the chocolate.

Use something flat--we used the bottom of a paper plate--to gently press down and weld the mosaic pieces together.

Step 5: Finishing

Remove from fridge. Peel top wax paper layer. If you can carefully remove from the dish without breaking it, you're basically done.

We found that the bottom wax paper layer was stuck to the glass dish. A few seconds in the microwave fixed that and I could remove the softened piece from the dish with a pie server. Then it went back to the fridge to harden again.

I also trimmed the edges with a sharp knife.