01 - In a small mixing bowl, beat the softened cream cheese, granulated sugar, and vanilla extract together until completely smooth and creamy. Gently fold in the fresh blueberries, taking care not to crush them.
02 - Lay out all 8 brioche slices on a clean work surface. Divide the cheesecake filling evenly among 4 slices, spreading it in a generous, even layer. Place the remaining 4 slices on top to form 4 stuffed sandwiches, pressing gently to seal.
03 - In a wide, shallow dish, whisk together the eggs, whole milk, ground cinnamon, and salt until fully combined and slightly frothy.
04 - Dip each stuffed sandwich into the egg custard, allowing it to soak for about 10 seconds per side. Ensure both sides are evenly coated but not oversaturated.
05 - Melt the butter in a large nonstick skillet or griddle set over medium heat. Working in batches if necessary, cook each sandwich for 3 to 4 minutes per side until deep golden brown and heated through to the center.
06 - Transfer the cooked French toast to serving plates. Dust generously with powdered sugar and finish with additional fresh blueberries, a drizzle of maple syrup, or a dollop of whipped cream as desired.