Preheat oven to 425 °F (220 °C). Butter and flour four 6 oz ramekins, tapping out excess flour.

In a microwave-safe bowl or double-boiler, melt butter with dark chocolate, white chocolate, and heavy cream until smooth. Let cool slightly.

In a mixing bowl, whisk together egg yolks, whole eggs, sugar, salt until pale and slightly thick.

Gently fold melted chocolate mixture into egg mixture, then stir in flour and ground pistachios until evenly combined.

Divide batter evenly into ramekins (about ¾ full).

Bake 10–12 minutes—edges should be set, centers still jiggly. Let cakes cool in ramekins 1–2 minutes.

Run a knife around edges, carefully invert each cake onto a plate.

Dust with powdered sugar and sprinkle additional chopped pistachios. Serve immediately—optional: with fresh raspberries or a scoop of vanilla ice cream.