01 - Preheat the oven to 350°F. Line a 12-cup muffin tin with paper liners or lightly grease each cup with cooking spray.
02 - In a large mixing bowl, whisk together the eggs, milk, protein powder, maple syrup, cinnamon, vanilla extract, and salt until completely smooth and no protein powder lumps remain.
03 - Add the bread cubes to the egg mixture. Toss gently with a spatula until all bread pieces are well coated and have absorbed most of the liquid. Allow the mixture to sit for 5 minutes to soak fully.
04 - Divide the soaked bread mixture evenly among the 12 muffin cups, pressing down lightly with the back of a spoon to compact the mixture in each cup.
05 - Sprinkle your choice of toppings (chopped nuts, mini chocolate chips, or fresh berries) evenly over each muffin.
06 - Bake for 20 to 25 minutes, or until the muffins are puffed, golden brown on top, and set in the center. A toothpick inserted into the center should come out clean.
07 - Let the muffins cool in the tin for 5 minutes before transferring to a wire rack. Serve warm or at room temperature.