Prep the skillet. Heat the oven to 350°F (175°C). Lightly butter a 9-inch oven-safe skillet (cast iron is ideal) or line with parchment.

Melt butter and chocolate. In a heatproof bowl, melt the butter and chopped dark chocolate together over a pan of simmering water or in short microwave bursts. Stir until smooth. Let it cool for 3–4 minutes.

Whisk in sugars. Add granulated and brown sugar to the chocolate mixture. Whisk until glossy and well combined.

Add eggs and vanilla. Whisk in the eggs one at a time, then the vanilla. Mix until the batter thickens slightly and looks shiny.

Fold in dry ingredients. Sift in flour, cocoa powder, and salt. Fold gently just until no dry streaks remain. Stir in chocolate chips if using.

Spread and add Creme Eggs. Scrape the batter into the skillet and smooth the top. Press Creme Egg halves into the batter, cut-side up. Don’t submerge them completely—leave some fondant showing.

Bake. Bake for 18–22 minutes until the edges are set and the center wobbles slightly. You want it fudgy, not cakey.

Rest, then serve. Let it sit for 5–10 minutes to settle. Spoon warm servings straight from the skillet with ice cream on top.