Prepare the filling:
In a mixing bowl, beat together the softened cream cheese, powdered sugar, and vanilla extract until smooth. If using jam, Nutella, or fresh fruit, layer it over the cream cheese mixture.
Assemble the sandwiches:
Spread the filling evenly onto one slice of bread, then top with another slice to create a sandwich. Repeat for the remaining bread slices.
Make the custard mixture:
In a shallow bowl, whisk together the eggs, milk, vanilla extract, cinnamon, and sugar until well combined.
Dip the sandwiches:
Carefully dip each sandwich into the egg mixture, ensuring both sides are evenly coated. Let the excess drip off.
Cook the French toast:
Heat a skillet or griddle over medium heat and melt 1 tbsp of butter. Cook each sandwich for 3-4 minutes per side, or until golden brown and cooked through. Work in batches, adding more butter as needed.
Serve:
Slice the stuffed French toast diagonally and top with powdered sugar, maple syrup, and fresh berries, if desired.