Butter six 4 1/2-inch-diameter tartlet pans with 3/4-inch-high sides and removable bottoms, then place them on a baking sheet.

Melt chocolate and butter in a heavy medium saucepan over low heat, stirring until smooth.

Remove from heat, then add espresso powder and salt and stir to blend well.

Cool to lukewarm, stirring occasionally.

In a large bowl, use an electric mixer to beat egg yolks, sugar (reserving 1 tablespoon), vanilla, and cinnamon until pale yellow and thick (about 5 minutes).

Fold 1/4 of the egg mixture into the chocolate mixture, then fold the chocolate mixture into the remaining egg mixture.

In another large bowl, beat egg whites until soft peaks form.

Add the reserved 1 tablespoon of sugar and beat just until firm peaks form.

Fold the egg whites into the chocolate mixture.

Divide the batter among the prepared tartlet pans.

Cover and chill for at least 1 hour and up to 4 hours.

Beat whipping cream in a large bowl until soft peaks form (can be made up to 4 hours ahead and refrigerated).

Position rack in center of oven and preheat to 400F.

Bake until edges are set and centers are still soft (about 11 minutes).

Cool on racks for 2 minutes.

Run a knife around the pan sides to loosen the cakes.

Remove the pan sides and transfer the cakes to plates.

Top each cake with a dollop of whipped cream.

Garnish with raspberries and mint (if desired).

Serve warm.