1 ¼cups(2 ½ sticks) unsalted butter, plus extra to butter ramekins
6large egg yolks
Extra powdered sugar and ice cream (optional)
Preheat the oven to 425 degrees F. Generously butter 6 1-cup ramekins.
In a medium saucepan, stir chocolate, 2 ½ sticks butter, espresso powder, cinnamon, cardamom, cloves, nutmeg and white pepper over medium-low heat until melted and smooth, stirring constantly. Cool slightly.
In a large bowl, whisk together eggs, egg yolks and vanilla. Whisk in powdered sugar until combined. Slowly stir in melted chocolate mixture then the flour.
Divide batter equally among the buttered ramekins, filling almost to the top. (Can be prepared 1 day ahead. Cover and chill. Let sit at room temperature 30 minutes before baking.)
Place ramekins on a rimmed baking sheet. Bake lava cakes in preheated oven 15-17 minutes, until batter has risen above the dish and top edges are dark brown and slightly crisp. The center should still be soft and runny. Bake 18-20 minutes for refrigerated batter.
Run a small knife around the cakes to loosen. Let rest 5 minutes.
Hold ramekin with a potholder, gently place a small plate atop the cake, and invert onto the plate. Repeat with the remaining cakes.
Dust cakes with powdered sugar and serve warm with ice cream, if desired.