1. Preheat oven to 450°F and position the oven rack in the center.

2. Place butter and chocolate in a heatproof bowl set over a saucepan of gently simmering water (double boiler). Melt together, stirring constantly, for 3–5 minutes until smooth and glossy. Remove from heat and allow to cool slightly.

3. In a medium bowl, sift together the powdered sugar and gluten-free flour.

4. In a separate bowl, whisk the egg yolks and whole eggs until pale, thickened, and slightly fluffy.

5. Add the melted chocolate mixture, eggs, vanilla extract, and salt to the flour mixture. Whisk until the batter is smooth and fully combined.

6. Generously grease two 8-ounce ramekins with softened butter, making sure to coat all sides. Dust with cacao powder and tap out any excess.

7. Divide the batter evenly between the prepared ramekins and place them on a baking sheet.

8. Bake for 10–12 minutes, until the tops are puffed and the edges are set, but the centers remain soft and slightly jiggly.

9. Remove from the oven and let the cakes cool for 3–5 minutes.

10. Run a knife gently around the edges of each ramekin to loosen.

11. Invert each ramekin onto a dessert plate and carefully lift to release the cake.

12. Serve immediately while warm, topped with powdered sugar, ice cream, or fresh berries if desired.