To prepare the ganache, place the two types of chocolate in a bowl. Heat the pareve whipping cream and pour it over the chocolate pieces. Wait one minute and mix well. Add the coffee granules and chocolate liqueur and mix again. If the chocolate doesn’t melt completely, place the bowl in the microwave for a few seconds to finish melting. Set aside.

To prepare the caramel cream, heat a wide, shallow pan over a medium flame for about two minutes. Pour an even layer of sugar into the pan and heat until it caramelizes, turning an amber color. Do not mix. Heat the heavy cream in the microwave and pour carefully over the hot caramelized sugar. (If you don’t heat the cream first, the sugar will clump when you pour it in.) Cook for another minute until you have a smooth caramel sauce.

Lower the flame, add the chopped white chocolate, and stir constantly until melted.

Add a beaten egg yolk and mix well until you get a thick, hot cream. Keep the flame low so that the yolk doesn’t congeal. Remove from the flame and cool.

Place the ganache into a piping bag with a smooth tip and fill the tartlet shells halfway. Sprinkle some ground hazelnuts over the ganache, and wait until it hardens a bit.

Transfer the caramel cream into a piping bag with a smooth tip and pipe over the ganache until the tartlets are filled. (If the cream cools, reheat it a little.)

Garnish with chocolate curls: Peel chocolate with a vegetable peeler to get thin curls. Arrange over the caramel cream while it is still soft. Freeze the tartlets and remove from freezer 15 minutes before serving.

Preheat oven to 325 degrees Fahrenheit (170 degrees Celsius). In a mixer bowl, whisk together margarine and confectioners’ sugar. Add egg yolk and water and mix until it is a smooth, creamy mixture. Add cocoa and flour. Continue mixing until soft, flexible dough.

Dust your work surface with a small amount of cocoa powder and roll out the dough to a thickness of about 3/4 inch (2 cm). Cut circles a bit bigger than the diameter of your tartlet pans. Line each pan with dough and even out the edges. You can stack them up to four tartlets high when baking. Bake for 20 minutes, then fill as above.