01 - Set oven to 425°F. Generously grease six 6-ounce ramekins with butter and dust lightly with cocoa powder, tapping out any excess.
02 - In a microwave-safe bowl, combine chopped dark chocolate and unsalted butter. Microwave in 20-second intervals, stirring after each, until mixture is fully melted and smooth. Allow to cool slightly.
03 - In a separate mixing bowl, vigorously whisk eggs, egg yolks, granulated sugar, vanilla extract, peppermint extract, and salt until pale in color and slightly thickened.
04 - Gradually pour the cooled chocolate mixture into the egg mixture, whisking continuously to combine. Gently fold in all-purpose flour just until no dry streaks remain.
05 - Divide the batter evenly among the prepared ramekins. Arrange ramekins on a baking sheet.
06 - Bake for 10 to 12 minutes, until the edges are firm but the centers remain slightly jiggly. Avoid overbaking to maintain the molten texture.
07 - Allow cakes to rest for 1 minute. Run a knife along the edges to loosen, then carefully invert each cake onto a serving plate. Top with a dollop of whipped cream, sprinkle with crushed candy canes, and garnish with mint leaves if desired.