Preheat oven to 375˚F.
Lightly grease a loaf pan with butter. Set aside.
Place all filling ingredients into a mixing bowl and whisk together until smooth.
Spread some of the raspberry mascarpone on half of the bread slices and sandwich together with the other half of bread slices.
In a shallow baking dish, whisk together cream, eggs, sugar, and vanilla.
Quickly dip each ‘sandwich’ into the creamy batter and transfer into the prepared loaf pan, stacking the sandwiches side by side until the pan is completely full (it’s okay to cram the slices together a little bit if necessary).
Pour the remaining batter over the loaf pan and allow pan to sit at room temperature for about 15 minutes.
Bake for 35 to 40 minutes or until golden brown on top with a soft center.
Allow French toast to cool, about 15 minutes before dusting with powdered sugar and serving with maple syrup.