Preheat the oven to 425°F (220°C). Generously butter four 6-ounce (180 ml) ramekins, then dust the inside lightly with cocoa powder, tapping out the excess. Place ramekins on a baking sheet.

Melt chocolate and butter

In a heatproof bowl set over (not in) simmering water (double boiler) or in short bursts in the microwave (20–30 seconds, stirring between bursts), melt the chopped bittersweet chocolate and 8 tbsp butter together until smooth. Remove from heat and let cool for 2–3 minutes.

Mix sugars and eggs

In a separate bowl, whisk together granulated sugar and brown sugar with the whole eggs and additional egg yolks until mixture is smooth and slightly pale, about 1–2 minutes. Add the vanilla and salt and whisk briefly.

Combine chocolate and egg mixture

Slowly whisk about a quarter of the melted chocolate mixture into the egg mixture to temper it, then whisk in the remaining chocolate until fully combined and glossy.

Fold in flour

Sift the all-purpose flour over the chocolate-egg mixture and gently fold with a rubber spatula until just incorporated and no streaks of flour remain. Do not overmix.

Portion and chill (optional)

Divide the batter evenly among the prepared ramekins (about 3.5–4 ounces / 100–115 g batter each). For more reliable molten centers, refrigerate the filled ramekins for 10–20 minutes; this helps the edges set before baking.

Bake

Bake on the center rack for 11–13 minutes. The edges should be set and the center still slightly jiggly. Exact time depends on oven and ramekin size — 11 minutes for very gooey centers, up to 13 minutes for slightly more set centers.

Rest and invert

Remove from oven and let the cakes rest for 1 minute. Run a small knife around the edges to loosen, then invert each ramekin onto a dessert plate and lift off carefully. If cakes don’t release easily, let them rest an additional 30 seconds and try again.

Finish and serve

Dust with powdered sugar if using, add a scoop of vanilla ice cream or a dollop of whipped cream, and serve immediately while the center is molten. Spoon on berry compote if desired.

Mixed Berry Compote (optional)

In a small saucepan over medium heat, combine the berries, granulated sugar, lemon juice, and water. Stir to combine and bring to a gentle simmer.

Simmer, stirring occasionally, until the berries break down slightly and the sauce thickens, about 5–7 minutes. Remove from heat and let cool slightly. Spoon a tablespoon or two over each lava cake when serving.