01 - Preheat oven to 425°F. Generously butter four 6-ounce ramekins and lightly dust with flour, tapping out excess.
02 - Melt chocolate and butter together in a heatproof bowl set over a saucepan of barely simmering water (double boiler), stirring until smooth. Remove from heat and let cool slightly.
03 - In a separate bowl, whisk eggs, egg yolks, and sugar until pale and thick, about 2 to 3 minutes.
04 - Stir the melted chocolate mixture into the egg mixture, then add vanilla and a pinch of salt. Sift in flour and fold gently until just combined.
05 - Divide batter evenly among prepared ramekins. Place ramekins on a baking sheet.
06 - Bake for 11 to 13 minutes, until the edges are set but the centers are still soft. Remove from oven and let stand for 1 minute.
07 - Meanwhile, combine raspberries, sugar, and lemon juice in a small saucepan. Cook over medium heat for 4 to 5 minutes until berries break down and sugar dissolves. Puree and strain through a fine sieve to remove seeds.
08 - Run a knife around the edges of each lava cake to loosen. Invert onto dessert plates.
09 - Dust with powdered sugar and garnish with fresh raspberries and mint if desired. Serve immediately with raspberry coulis.