meringues:
1 egg white
45 g sugar
3/4 ts instant espresso powder
3/4 ts cornstarch
filling:
30 g chocolate, 75%
30 g whipping cream
Combine cornstarch and espresso powder, set aside. Whip the egg whites to soft peaks. Then, while beating, slowly add the sugar. Continue beating until the sugar is dissolved and the mixture is very thick and glossy. Carefully fold in the espresso mixture.
Line a baking sheet with parchment paper. Prepare a pastry bag with a small plain (round) tip. Fill the mixture into the bag and pipe small baskets/bowls (1.5-2 cm diameter). The easiest way is to pipe a continuous spiral: Starting in the center of the bottom, pipe a spiral outward and end by making 2 or 3 times a circle at the edge.
Bake in preheated oven at 120 deg C for about 30-40 minutes. Let cool on a wire rack.
For the filling, heat the whipping cream (don't bring to a boil). Add the chocolate and stir well until it is melted and the mixture is smooth. Put into a pastry bag with small plain tip and fill into the meringue baskets.