Using a small sharp knife, cut a 3-inch pocket about 2 inches deep in the top-crust side of each bread slice, cutting to but not all the way through to the other side. For filling, in a medium bowl beat mascarpone with an electric mixer on medium to high speed for 30 seconds. Add 2 tablespoons granulated sugar and the 1/2 teaspoon vanilla. Beat until smooth. Divide mascarpone mixture evenly among bread slices, spooning it into the pocket of each bread slice. Place bread slices in a 2-quart rectangular baking dish; set aside.
In a medium mixing bowl whisk together eggs, milk, honey, coffee crystals, and the 1 teaspoon vanilla. Slowly pour the egg mixture over bread slices. Using the back of a wide spatula, press bread down lightly to soak with egg mixture. Cover and chill for 2 to 24 hours, turning bread slices over once or twice during chilling.
Preheat oven to 350 degrees F. Line a 15x10x1-inch baking pan with parchment paper. Arrange bread slices in the prepared baking pan. Bake, uncovered, for 30 to 35 minutes or until golden brown, turning once halfway through baking.
Before serving, sprinkle with powdered sugar and drizzle with hot fudge topping. If desired, garnish with fresh mint sprigs and/or fresh raspberries.