Prepare the Custard Mixture:
In a medium mixing bowl, whisk together the eggs, milk (or cream), sugar, vanilla extract, and cinnamon (if using) until well combined.
Heat the Skillet:
Place a non-stick skillet or griddle over medium heat and melt a tablespoon of butter. Allow the butter to coat the surface evenly.
Soak the Brioche:
Dip each slice of brioche into the egg mixture, ensuring both sides are coated but not soaked too long. The rich brioche will absorb the custard mixture quickly.
Cook the French Toast:
Place the soaked brioche slices in the skillet and cook for 2-3 minutes per side, or until golden brown and crispy. Add more butter to the skillet if needed between batches.
Serve and Enjoy:
Serve the French toast immediately with a drizzle of maple syrup, fresh berries, whipped cream, or powdered sugar.