Preheat oven to 425.

Butter six soufflé dishes very well. The best way to do this is to soften butter (or use vegetable shortening or margarine) and a wadded up paper towel, smear a large amount inside each dish, making sure to get into the edges.

In a saucepan over medium heat, add the chocolate and butter. Stir constantly until chocolate is melted, about 5 minutes. Remove from heat. Add beer, and peppermint extract, stir to combine.

In a separate bowl, whisk the eggs, yolks and powdered sugar.

Pour chocolate mixture over egg mixture, stir to combine.

Sprinkle cocoa powder, espresso powder and flour over chocolate mixture, stir until just combined.

Divide equally between souffle dishes, making sure not to fill more than 2/3 full. Press about 4 to 5 chocolate chips into the very center of each cake (can be made one day ahead, cover and chill).

Bake at 425 until the outside is set, but the center is still liquid, about 9 minute no more than 13. (Note: Glass baking dishes cook much faster then ceramic dishes. Take these out of the oven when it looks as if they "need a few more minutes," you want a very runny center.)

Run a butter knife around the edge of the cake. Place a plate on top of each ramekin, turn upside down, lift ramekin to reveal cake. Serve immediately.