Preheat the oven to 350°. Lightly butter eight 3-inch-wide, 2-inch-deep metal rings or cleaned 6-ounce tuna cans, bottoms removed; coat with flour. Butter a large rimmed baking sheet and arrange the molds on the sheet.
Spread the sliced almonds on another rimmed baking sheet and toast in the oven for about 6 minutes, stirring a few times, until golden brown. Transfer the almonds to a plate and let cool completely. Set aside 1/2 cup for garnish; pulse the remaining almonds in a food processor until finely ground. Leave the oven on.
In a large bowl, using an electric mixer, beat the butter with 2/3 cup of the sugar on moderately high speed until light and fluffy, about 5 minutes. Beat in the egg yolks, 1 at a time, until thoroughly incorporated. Fold in the ground almonds and the chocolate.
In a large bowl, beat all 6 egg whites until soft peaks form. Add the remaining 2 tablespoons of sugar and beat until firm, glossy peaks form. Fold one-third of the beaten whites into the chocolate mixture to loosen it, then fold in the remaining whites just until blended. Spoon the batter into the prepared molds, filling them three-quarters full. Bake the chocolate-almond cakes for about 25 minutes, or until risen and just set in the center. Let the cakes cool slightly in the molds.
Run a thin knife around the sides of the molds, then lift them off the cakes. Transfer the cakes to individual plates. Garnish the tops of the cakes with the reserved toasted almonds and dust them with confectioners&339; sugar. Spoon a dollop of whipped cream alongside and serve.
For this rich but not overly sweet cake, try a Sauternes or a much more affordable Muscat.