Sometimes it may be difficult to understand the background for some cake name. Regarding fragilities, one may feel fairly sure. These cakes are in fact delicate and fragile, just what one in French and English would call “fragile.”
100 g [3,5 oz] hazelnut kernels
175 g [6,2 oz] icing sugar
4 egg whites
2 tablespoons flour
 Grind the hazelnut kernels on an almond grinder, mix them with the flour and powdered sugar and fold the mixture into the whipped egg whites.
 Pour the dough into a greased and sprinkled baking tray. Bake the cake for about 15 minutes at 175° C / 345° F and let it cool on a rack. Then you fill it with a butter cream made of:
4 egg yolks
100 g [3,5 oz] sugar
1 teaspoon flour
2 dl [0,4 pt] milk
4 teaspoons strong coffee
150 g [5,3 oz] butter.
 Stir the egg yolks well with the sugar in a small saucepan. Stir in the flour and then the milk. Bring to a boli, stirring constantly and allow the mixture to thicken.
 Pour the cream into a bowl and let it get cold. Stir in the coffee and 150 g / 5,3 oz softened butter. Cut the cake in two layers and fill it with the cream. Let cake rest for a few hours before serving.
 Sprinkle with sifted powdered sugar and cut the cake into squares just before serving.