In a medium bowl add the mascarpone, powdered sugar, 2 tablespoons winter ale and salt. Beat with a hand mixer until well combined.
Slice the bread into 3-inch slices (about 8 total).
Using a sharp knife, make a slit in the center of the bread slices, forming a pocket for the filling.
In a medium bowl add the eggs, cream, ½ cup winter ale, vanilla, and sugar, whisk until well combined.
Melt the butter in a large skillet over medium high heat.
One at a time spoon the filling into the bread slices. Dip in the egg mixture, making sure to coat well. Remove from the bowl allowing the liquid to drain off the bread.
Place the French toast in the hot pan, cook on each side until golden brown, about 4 minutes per side.
Serve warm.