Step 1

Grease four 8-oz ramekins* with butter and dust inside with flour, tapping out excess flour, just like you would with a cake pan.

Step 2

Set a mixing bowl over a medium saucepan with about 1 cup water (the bowl should not touch the water). In the bowl, combine 6 oz semisweet chocolate and sliced butter. Keep water at a simmer and use a spatula to stir together until the chocolate and butter are melted and well combined then carefully remove from heat and set aside while making egg mixture.

Step 3

Combine 2 eggs, 2 yolks, 1/4 cup sugar, and 1/4 tsp salt and beat with an electric mixer on high speed 5 minutes (using egg beaters or whisk attachment) until whipped, thick and light yellow.

Step 4

Pour warm chocolate mixture into the egg mixture along with 1 tsp vanilla extract. Fold until mostly combined. Add 3 Tbsp all-purpose flour and fold until fully incorporated.

Step 5

Divide between 4 ramekins and bake at 450˚ for 10-12 minutes (in a very hot oven) until outsides are firm and dry and centers are soft with just the slightest jiggle in the center.

Step 6

Cool 1 minute then gently loosen cakes with a small knife (if needed). Immediately invert onto plates to untold. Dust with powdered sugar and serve right away.