In a mixing bowl, combine the softened cream cheese and sugar. Use a whisk or fork to blend until smooth and creamy. Stir in the blueberry preserves until fully incorporated. Set this delightful filling aside while you prepare the bread.
Take one slice of brioche bread and spread a generous layer of the cream cheese mixture on one side. Top with another slice of brioche to create a sandwich. Repeat this process until you have four stuffed sandwiches.
In a large bowl, whisk together the eggs, milk, and vanilla. Add a sprinkle of ground cinnamon to the mixture for added warmth and depth of flavor.
Carefully dip each stuffed sandwich into the egg mixture, ensuring that both sides are well-coated. Allow the excess to drip off before placing them onto a plate.
In a frying pan or griddle, melt 1 tablespoon of butter over medium heat. Once melted and bubbling, add two of the stuffed sandwiches to the pan. Cook for 3-4 minutes on each side, or until golden brown. Repeat this process with the remaining sandwiches, adding more butter as needed.
Once cooked, slice the stuffed French toast in half to reveal the creamy center. Serve warm, drizzled with maple syrup and topped with fresh blueberries for a burst of flavor and color.