Finely chop 2/3 pound of the milk chocolate and melt it over a hot but not boiling bain-marie: using a probe thermometer, check that it does not exceed 115°F. Then add in the finely chopped dark chocolate, turn off the heat, and mix with a spatula until it is completely melted. Pour a third onto a marble work surface and move it around with the spatula so it cools: as soon as it begins to set, add it back into the rest of the chocolate and, stirring very gently, ensure that the temperature reaches 88°F.|Turn a baking tray over and cover it with a sheet of parchment paper. Pour the chocolate into 6 faceted silicone molds (2-inch height). Ensure it sticks to the walls so they are perfectly covered. Let any excess chocolate drip out, then place the molds upside down on the baking tray. After 40 minutes, carefully trim the edges of the molds using a knife.|Place them back on the tray upside down and let them set for another 2 hours; finally, remove the chocolate cups from the molds. Soak the gelatin sheet in water. Over a hot bain-marie, melt the rest of the milk chocolate together with the 3 espresso shots and the milk; add in the drained gelatin and mix until it has melted completely. Let it cool to room temperature, then place it in the refrigerator for 30 minutes.|Partially whip half the cream, then gently fold it into the mixture; once it is thoroughly incorporated, finish whipping with an electric hand mixer until you obtain the desired consistency. Fill the chocolate cups with the cappuccino mousse and place them in the fridge for at least 1 hour. Partially whip the other half of the cream and use it to top the cups like foam, then dust with cocoa powder.