5 (2 by 2 1/4-inch) round molds and an electric mixer
Preheat the oven to 400 degrees F.
Butter the round molds with the unsalted butter and dust with cocoa powder, tapping out excess cocoa.
Melt the extra bitter chocolate and the unsalted butter in a double boiler. In an electric mixer, beat the eggs, yolks, and sugar until light and fluffy. Stir in the chocolate/butter mixture. Add all the flour and mix until just incorporated.
Pipe or carefully spoon the batter into the prepared molds, filling no more than 1/2 full.
Place the filled molds on a baking sheet. Refrigerate for a minimum of 20 minutes. The batter will hold overnight in the refrigerator after it's been put into the molds. Bake for 7 to 9 minutes.
The tops will have cracks, the sides will be set, but the centers will be very soft.
Serve immediately and drizzle with Espresso Creme Anglaise.
Espresso Creme Anglaise:
Whisk the yolks and the sugar together until thickened and pale yellow.
In a small pot warm the cream just to the boiling point over medium heat.
While whisking, add some of the hot cream into the egg mixture. Pour into the pot with the rest of the cream and stir with a wooden spoon or rubber spatula until the mixture thickens enough to coat the back of the spoon. Add the espresso. Refrigerate until ready to use.