Break the chocolate bars along the cracks and melt in a 50℃ double boiler.
Warm the heavy cream, mizuame, and instant coffee in a pot. Turn the heat off when it's just about to boil.
Pour the mixture from Step 2 into the bowl from Step 1 and fold in using a rubber spatula. Melt the butter in room temperature, and mix well into the chocolate with the rum to finish.
Pour the chocolate into a mold lined with parchment paper. Chill in the fridge to set.
When set, remove the chocolate from the mold and cut into desired sizes. Sprinkle the cocoa powder using a tea strainer.
The butter and mizuame is to make the truffles more smooth. Please adjust the amount of mizuame to the sweetness of the chocolate bar. The mizuame itself is optional.
If you'd like a harder result, please reduce the amount of the heavy cream. Here's the cocoa powder that I used.
Rich Chocolate Mousse Recipe ID: 1709249.
Story Behind this Recipe
In this recipe, I added some coffee into my regular truffles. I made it with dark chocolate since I don't like mine to be too sweet. Actually, I just came up with this recipe. You can also melt the chocolate in a microwave.
The low-fat cream is substitutable with dairy heavy cream. I changed the amount of chocolate when I updated this recipe. When using 180 g of chocolate, use 100 ml cream, 20 g butter, and 2 teaspoon mizuame. Step 4: You can also use a sheet of plastic wrap for the parchment paper.