Whisk together the milk, eggs, brown sugar, cinnamon, and vanilla in a large bowl.
Dip the brioche bread into the egg mixture. Lightly press down to coat both sides.
Melt the butter in a large skillet over medium heat.
Transfer the soaked bread to skillet and cook on each side until golden brown. Repeat with rest of bread slices.
Serve with your choice of french toast toppings and enjoy!