1. Begin by cutting or tearing day-old French bread into 1-inch cubes to prepare about 6 to 12 cups, depending on the number of muffins you want to make.

2. In a large bowl, whisk together 6 large eggs.

3. Add 1-2.5 cups of milk to the eggs, adjusting the quantity based on your preferred richness, and optionally substitute part of the milk with heavy cream for a creamier texture.

4. Mix in 1/2 to 1/3 cup of granulated sugar, 2 tablespoons of maple syrup, 1-2 tablespoons of vanilla extract, 1-2 teaspoons of cinnamon, and a pinch of salt (if desired) to the egg mixture. Whisk well until smooth.

5. Gently fold the bread cubes into the prepared custard mixture, ensuring they are evenly coated. Allow the bread to sit for a few minutes to absorb the liquid.

6. Preheat your oven to 350°F (175°C).

7. Grease a 12-cup muffin tin generously with butter or cooking spray to prevent sticking.

8. Scoop the custard-soaked bread cubes into each muffin cup, filling them to the top.

9. In a separate bowl, mix together cold butter, brown sugar, all-purpose flour, cinnamon, and a pinch of salt to create the streusel topping.

10. Sprinkle the streusel mixture evenly on top of each muffin for a crunchy finish.

11. Bake the muffins in the preheated oven for 25-30 minutes or until the tops are golden brown.

12. Once baked, allow the muffins to cool slightly before serving.

13. Optionally, drizzle the French Toast Muffins with maple syrup, dust them with powdered sugar, or top them with whipped cream for added sweetness and presentation.

14. To store leftovers, place them in an airtight container in the refrigerator for up to 5 days or freeze individually wrapped muffins for up to 3 months.

15. When reheating, bake muffins in the oven at 350°F for a few minutes or heat them in the microwave, covering them with a damp paper towel to maintain moisture.