Beat eggs, gradually adding the sugar, and continue beating until light and fluffy. Mix in the nuts and flour only until blended, then fold in the cooled, melted butter.
Turn into a greased and floured 9-inch springform pan and bake in a 325 degrees F oven for 40 to 60 minutes, or until cake tests done. Cool cake for about 15 minutes, then remove from the pan and cool on a rack.
While cake is cooling, stir all of the filling ingredients together over medium heat until smooth, and let the mixture come to a boil. Cool.
When the cake is cold, split it in half and fill with filling mixture. Replace top layer.
Whip cream until very thick, and add sugar and flavoring. Spread on cake or use a pastry bag with a fluted tube and your imagination.