Add the bourbon, sugar, and stout to a saucepan. Simmer until sugar has dissolved.

Add the cherries to a re-sealable jar, pour bourbon/beer mixture over the cherries. Allow to sit at room temperature for one hour. Seal and refrigerate until ready to use, can be made several weeks in advance.

Heat the oven to 375°F.

Place butter, stout, and chocolate in the top of a double boiler (or a metal bowl set over a pot of water) over gently simmering water. Stir frequently until melted, remove from heat and allow to cool slightly.

In the bowl of a stand mixer add the egg whites, salt, and cream of tartar, building up speed, beat on high until soft peaks form. While the mixer is running add the sugar a bit at a time, beat until stiff peaks form.

In a large bowl stir together the egg yolks, cornstarch, and flour. Beat on high until light and slightly fluffy.

Slowly pour the chocolate mixture into the egg yolk mixture, beating until completely combined, scraping the bottom to make sure the mixture is well incorporated.

About 1/3 at a time, gently fold the egg whites into the chocolate mixture using a spatula. Stir until egg whites are well combined with the chocolate mixture.

Grease two large (10oz) ramekins or oven-safe bowls with butter until well coated.

Add the batter evenly between the two ramekins.

Bake for thirty minutes or until the top has puffed and looks dry. Remove from oven and allow to cool to room temperature before removing from ramekins.

Add the cherries to a small pot or skillet. Pour the Cointreau over the cherries. Using a kitchen torch or long match, light the liquid on fire. Swirl until to distribute the flame. Allow to flambé for about 2 minutes, then add a lid to extinguish the flame. Pour the liquid and the cherries evenly over the cakes. Serve immediately.