In a medium bowl, stir together nuts, flour, and baking powder.
In a blender or food processor, combine eggs and sugar; cover and blend or process unil smooth. Add nut mixture. Cover and blend or process until smooth.
Spread batter evenly in two greased and lightly floured 8-inch round cake pans.
Bake in a preheated 350º oven for 20 to 25 minutes or until cakes spring back when lightly touched. Cool in pans on wire racks for 10 minutes. Remove from pans. Cool on wire racks.
Spread Mocha Frosting on each layer; stack layers. Loosely cover and chill frosted cake for 2 to 24 hours. If desired, top with chocolate curls.
In a chilled small mixing bowl, dissolve 1 tsp. instant coffee crystals, crushed, in 1 cup whipping cream; beat with chilled beaters of an electric mixer on low speed until slightly thickened. Add 1/3 cup sugar, 1/4 cup cocoa powder, and vanilla. Beat just until stiff peaks form.