To make the almond meringue: mix together ground almonds, potato starch or cornstarch, and all but 6tablespoons of the sugar. Stiffly whip the egg whites, add the remaining sugar and continue whipping for 30 seconds or until the mixture forms a glossy meringue that holds peaks. Fold in the almond mixture in 3 batches.
Pipe 3 meringue rounds following the instructions. Bake in the preheated oven until crisp and dry, 40-50 minutes. While meringue is still warm, trim rounds neatly with a sharp knife. Transfer them to a rack to cool. Make butter cream and flavor it with praline or coffee.
To assemble the cake: spread about one quarter of the butter cream on a meringue layer. Add the second layer, spread with more butter cream and top with the remaining meringue layer. Spread remaining butter cream over the top and sides, reserving 2-3tablespoons.
Sprinkle the top thickly with confectioners’ sugar and press chopped almonds around the edge of the cake. Make a paper piping cone, fill it with the reserved butter cream and pipe the word “succès” across the top.