- 4 tablespoons (55 grams) unsalted butter, cut into chunks, plus more for dishes
- 2 teaspoons cocoa powder, plus more for dusting
- 3 ounces (85 grams) bittersweet chocolate, roughly chopped
- 1/8 teaspoon fine sea salt or a couple pinches of flaky salt
- 1 to 2 tablespoons (13 to 25 grams) granulated sugar (see Note)
- 1 large egg
- 1 egg yolk
Place 4 tablespoons butter and chocolate in a medium heatproof bowl and — either in the microwave or set over a pot of gently simmering water — melt the butter and chocolate about two-thirds of the way, then whisk until it finishes melting. (This ensures it’s not too hot to add other ingredients.) Whisk in sugar and salt. Whisk in egg and yolk and beat a good 20 to 30 extra times, to ensure mixture is smooth, glossy, and a bit lightened.* Add 2 teaspoons cocoa powder and whisk until combined.
Divide between two baking dishes. Bake 7 to 9 minutes (7 will be the most molten in the center, 9 the least but still gooey) and transfer to a cooling rack for 1 minute. Wearing pot holders, place a small dessert plate over your first ramekin. Flip it onto the plate, count to ten, then lift the cup off. Repeat with second cake. Dust with cocoa powder or powdered sugar. Serve with barely sweetened whipped cream, a little ice cream, berries, or absolutely nothing at all. Eat immediately.
*Updated to note: This is really important! Don’t skip the extra 20 to 30 whisks around the bowl. For reference, this is how it looks when it’s not whisked enough (yes, been there, done that) and this (glossy and smooth) is how it looks when it is.
Do ahead: You can make the batter and fill the prepared cups, then refrigerate until you want to bake them. They can go into the oven directly from the fridge, but will need to bake 1 to 2 minutes longer.