Line an 8 by 4-inch loaf pan or 6-inch gratin dish with plastic wrap. To prepare the ganache, put the chocolate in a bowl. Bring the cream to a boil in a small saucepan and pour the hot cream over the chocolate. Let stand until the chocolate begins to melt, about 2 minutes, then whisk until smooth.
Pour the ganache into the loaf pan or gratin dish and refrigerate until firm, about 1 hour. When the mixture has set, unmold, and cut out 6 (1 1/2-inch) rounds (you can use a knife or a cookie cutter). Refrigerate until ready to use (up to 5 days).
Preheat the oven to 350 degrees F. Butter a muffin pan and set aside.
To make the cakes, in the top of a double boiler, or in metal bowl suspended over a pot of simmering (not boiling) water, melt the chocolate. Whisk in the softened butter and turn off the heat. Let cool for 5 minutes, then whisk in the egg yolks, one at a time.
Sift together the almond and cake flours and fold the flours into the chocolate mixture.
Using an electric mixer, beat the egg whites to soft peaks. Sift in the confectioners' sugar and continue beating to stiff peaks. Fold 1/3 of the egg white mixture into the chocolate mixture, then gently fold in the remaining whites in two additions.
Scoop or pipe a 1/4-cup measure of cake batter into each muffin tin.
Place a ganache round in the center of each muffin cup, then spoon in enough batter to cover. Bake the cakes for 20 minutes, or until the tops are firm. Allow the cakes to rest for 1 minute before serving.