Prep the pan and oven: Heat the oven to 350°F (175°C). Grease a 9-inch oven-safe skillet (cast iron works best). If your skillet is larger, watch the bake time.

Brown the butter: Melt butter in a light-colored saucepan over medium heat. Stir until it foams, then turns amber with brown specks and smells nutty. Remove from heat and let cool 5–7 minutes so it won’t scramble the eggs.

Whisk sugars and butter: In a mixing bowl, whisk the brown sugar and granulated sugar with the browned butter until glossy and combined.

Add eggs and vanilla: Whisk in the egg, egg yolk, and vanilla until smooth and slightly thick. The mixture should look shiny.

Combine dry ingredients: In a separate bowl, whisk flour, cornstarch, baking powder, and salt. Fold into the wet ingredients just until no dry streaks remain. Do not overmix.

Fold in chocolate: Gently fold in crushed mini eggs and white chocolate (if using), reserving a small handful for the top.

Fill the skillet: Spread the batter evenly in the greased skillet. Press a few extra mini eggs on top for color and crunch.

Bake: Bake 16–22 minutes, until edges are set and golden, but the center still looks slightly underbaked. A toothpick should come out with moist crumbs, not wet batter. Pull earlier for gooey, later for chewy.

Rest briefly: Let it sit 5–10 minutes. It will firm up slightly but stay soft and fudgy in the middle.

Serve warm: Top with ice cream and dig in straight from the skillet. For cleaner slices, wait 20 minutes, then cut.