Molten Chocolate Cakes

8 tbsp. unsalted butter, room temperature (plus more for muffin tins)
Cocoa powder, for dusting
2 2/3 c. semisweet chocolate chips, melted
1/2 c. granulated sugar, plus more for muffin tins
6 large eggs
2/3 c. all-purpose flour
1 tsp. vanilla
2 tsp. espresso powder
1/2 tsp. salt
Confectioners' sugar, for dusting
  1. .

  1. Preheat oven to 400 degrees F. Generously butter 12 cups of a standard muffin tin. Dust with cocoa powder, and tap out excess. Set aside.
  2. In a large bowl, cream the butter and granulated sugar until fluffy with a hand mixer. Add eggs one at a time, beating well after each addition. Gradually beat in flour and salt until just combined. Stir in chocolate until evenly incorporated.  Batter can be made 24 hours ahead of time and kept in refrigerator  Bring to room temperature before baking
  3. Divide batter evenly among prepared muffin cups. Bake for 8-9 minutes, just until tops of the cakes no longer jiggle. Remove from oven and let stand 5 minutes. Place a large baking sheet on top of the muffin tin. Hold both pans together and flip them to invert cakes onto to the baking sheet. Quickly transfer to serving plates, bottom sides up. Dust with confectioners' sugar. Serve immediately