In a small bowl, whisk together the sugar and cinnamon. Set the bowl right next to the stove so it's easy to reach when you start cooking.
¼ cup sugar, ½ teaspoon cinnamon
For the French Toast
If your brioche is fresh, slice it ¾ to 1 inch thick and let the slices sit out for a few hours, or dry them in a 200°F oven for 10 minutes.
8 slices of brioche
In a large measuring cup, whisk together the eggs, milk, maple syrup, vanilla, cinnamon and salt until smooth.
4 large eggs, 1 cup whole milk, 1 tablespoon maple syrup, 1 teaspoon vanilla extract, ½ teaspoon cinnamon, pinch of salt
Pour the custard into a shallow bowl or pie plate.
Heat a large skillet or griddle over medium heat and add 1 tablespoon of butter. Let it melt and foam.
1 to 2 tablespoons butter
Dip each slice of brioche into the custard for 10 to 15 seconds per side.
Add the brioche slices to the pan, leaving a little space between each one. Cook for 2 to 3 minutes, until the bottoms are deeply golden brown.
Flip each slice and immediately sprinkle a generous pinch of cinnamon sugar across the top. Cook for another 2 to 3 minutes, until the second side is golden and the centers feel springy when you press them gently.
Transfer to plates and serve right away with pure maple syrup and fresh berries. Add more butter to the pan as needed between batches.
Notes
The bread you choose matters - Day old or slightly dry brioche works best. Fresh slices fall apart in the custard - if your loaf is fresh, let the slices sit out for a few hours.Don't over soak - 10 to 15 seconds per side is all you need. Any longer and the bread fills up with too much custard, leaving you with eggy, undercooked French toast.Watch the heat - Keep the pan just below medium so that the custard has time to set before the outside browns. If your slices are getting very dark quickly, turn down the heat. Make ahead - Whisk the custard up the night before and keep it covered in the refrigerator. In the morning, give it a quick whisk and you're ready to dip and cook.