Prep the oven and crust. Preheat the oven to 350°F (175°C). If using a refrigerated pie crust, fit it into a 9-inch pie dish and crimp the edges. Chill the crust in the fridge while you prepare the filling to help it keep its shape.

Melt butter and chocolate. In a heat-safe bowl, melt the butter and 1 cup of chocolate chips together over a pot of simmering water or in the microwave in 20–30 second bursts. Stir until smooth and glossy. Let it cool slightly so it doesn’t scramble the eggs.

Whisk in sugars. Add granulated sugar and brown sugar to the melted chocolate mixture. Whisk until combined and slightly thickened. This helps create that classic crackly top.

Add eggs and vanilla. Whisk in the eggs one at a time, beating well after each addition. Mix in the vanilla. The batter should look shiny and smooth.

Combine dry ingredients. In a separate bowl, whisk together flour, cocoa powder, salt, and baking powder. This prevents clumps and keeps the texture even.

Fold it all together. Gently fold the dry mixture into the wet batter until just combined. Do not overmix. Fold in the optional extra chocolate if using.

Fill the crust. Pour the batter into the chilled pie crust and smooth the top with a spatula. For a bakery finish, sprinkle a pinch of flaky sea salt over the surface.

Bake. Bake for 35–45 minutes, until the edges are set and a toothpick inserted 2 inches from the edge comes out with a few moist crumbs. The center should jiggle slightly but not look soupy.

Cool before slicing. Let the pie cool at least 30–45 minutes so it sets enough to slice cleanly. For a molten center, serve warm. For cleaner slices, cool to room temperature.

Serve. Enjoy as is, or top with vanilla ice cream, whipped cream, or a drizzle of warm chocolate sauce.