Chop the chocolate into small bits and set aside.
Mix together the mascarpone and almond extract and set aside.
Cut the panettone or brioche into 16 equal slices discarding the ends. Remove the crust squaring the slices off as much as possible. Lay 8 slices of brioche out on the work surface. Spread the mascarpone mixture on the slices, then sprinkle over the chocolate bits. Cover with the remaining slices of brioche to create sandwiches. You may wrap the sandwiches up in plastic film and refrigerate for a few hours or proceed with recipe.
In a mixing bowl, whisk together the eggs, sugar, vanilla, and 1 1/2 cups of the heavy cream. Set aside. Whip the remaining cup of heavy cream into stiff peaks, cover, and refrigerate until ready to use.
Melt 1 tablespoon of butter in a large nonstick skillet over moderate heat. Dip each sandwich into the egg mixture to saturate the bread allowing any excess to drip back into the bowl. Transfer to the skillet. Dip and add only as many sandwiches as fit into the skillet in 1 layer. Saute gently until the bottom is golden, about 3 minutes. With a spatula turn the sandwiches and continue to saute until the second side is golden and the chocolate in the center has melted. Transfer the sandwiches to a warm platter as they are done. Add more butter to the skillet and continue to dip the sandwiches in the egg mixture and saute them until all the sandwiches are cooked.
Serve the sandwiches on individual dessert plates and garnish with a dollop of whipped cream and a dusting of confectioners' sugar.