1 cup unblanched whole almonds, coarsely chopped
2 cups whole milk
4 egg yolks
2/3 cup sugar
1 teaspoon vanilla extract
10 ounces best-quality semisweet chocolate, chopped
2/3 cup dark brown sugar
1/2 cup unsalted butter
4 eggs, separated
1 1/2 teaspoons vanilla extract
1/2 cup slivered almonds, toasted and ground
6 tablespoons all-purpose flour
1/4 teaspoon kosher salt
To make the creme anglaise, preheat the oven to 350 degrees. Place the almonds on a baking sheet and toast until nicely browned, stirring twice, about 10 minutes; watch carefully to prevent burning. Place in a saucepan with the milk and bring just to a boil. Remove from heat, cover and let stand 15 minutes.
Whisk the egg yolks and sugar together until pale yellow. Bring the milk mixture back to a simmer. Whisking constantly, add the milk to the yolk mixture. Return sauce to pan over low heat and cook, stirring constantly, until thick enough to coat the back of a spoon; do not let it simmer. Strain through a fine sieve. Stir in the vanilla. Refrigerate until cold.
To make the cake, preheat oven to 350 degrees. Butter a 10-inch springform pan. Place chocolate, brown sugar and butter in a metal bowl over a pan of barely simmering water until melted. Mix well. Stir in egg yolks and vanilla, then almonds, flour and salt.
Whip egg whites until firm but not dry. Stir 1/3 of the whites into chocolate mixture. Fold in remaining whites. Scrape batter into prepared pan and bake until a toothpick inserted into center comes out only slightly wet, about 30 minutes. Cool.
To serve, spoon sauce onto each plate and top with a slice of cake.