Preheat oven to 300 degrees and place oven rack in middle position.
Place chocolate in a heatproof bowl. In a medium saucepan over medium-high heat, bring cream, milk, and a pinch of salt just to a boil. Pour scalded milk over chocolate and let stand for 3 to 5 minutes, then whisk until smooth.
In a separate bowl, whisk together egg yolks, sugar, and nutmeg. Slowly and carefully pour warm chocolate mixture into egg mixture, whisking constantly. Pour custard through a fine mesh sieve into a large glass measure with a pour spout. Let custard cool slightly.
Line the bottom of a 9-by-13-inch casserole dish with a folded kitchen towel and arrange six 6-ounce ramekins on top of towel. Divide custard evenly among ramekins, then pour enough hot water into casserole dish to reach halfway up ramekins. Tightly cover pan with aluminum foil and bake for 50 to 55 minutes, or until the custards are set but still slightly wobbly in centers.
Transfer ramekins to a wire rack to cool completely, uncovered, for about 1 hour. Chill ramekins, covered, for at least 2 hours before serving. When ready to serve, garnish with raspberries, whipped cream, and mint leaves.
Cook's Note: The pots de creme can be kept in the refrigerator, covered, for up to days before serving.