Melt the Dark Chocolate: First, you need to melt your dark chocolate. I usually put it in a glass bowl over a small pot of simmering water, but you can use the microwave in 30-second bursts if you are in a hurry. You want to stir it gently until it is completely smooth and glossy without any lumps left. Be careful not to let any water get into the chocolate, or it might seize up and get grainy, which is the last thing we want for a silky mousse.
Blend Until Smooth: Now, grab your high-speed blender and add in the leftover rice, the hot water, your vanilla extract, and that beautiful melted chocolate. Turn the blender on to its highest setting and let it run until the mixture is perfectly smooth and looks like a dark, thick velvet. This is the part where the rice magically disappears! You want to make sure there are absolutely no tiny bits of rice left at all, so don't be afraid to let it run for an extra minute just to be safe.
Portion and Chill: Once the mixture is totally smooth and smells incredible, pour it evenly into your favorite dessert cups. I like to use glass ones so you can see the rich color. Place them in the refrigerator for at least two hours to let them rest. During this time, the melted chocolate and the starch from the rice will work together to thicken the mousse into a dense, creamy pudding that is firm enough to hold its shape on a spoon but still soft enough to melt in your mouth.
Dust and Serve: When the two hours are finally up and the mousse feels firm to the touch, take the cups out of the fridge. Use a small sifter to lightly dust the top of each serving with a bit of cocoa powder. This adds a professional, finished look and a little extra punch of chocolate flavor that is just lovely. Serve it immediately while it is still nice and cold, and enjoy the look on everyone's face when you tell them the secret ingredient is just a cup of leftover rice!
