Mini-Cakes with Walnuts and Chocolate

Coarsely chop the chocolate, then put it in a bowl and melt it in a double boiler, mixing it together with the sugar, 1/3 cup soft butter and the egg yolks. Remove the mixture from the double boiler and let it cool thoroughly. Meanwhile, beat the egg whites and a pinch of salt until very stiff, then gently stir them into the chocolate mixture. Lastly sift in the flour. Distribute the batter into 12 paper ramekins brushed with melted butter, add the chopped walnuts, and then bake the cakes in the oven at 350 °F for 25 minutes. Serve the mini-cakes while still slightly warm, without removing them from the ramekins.