Pre-heat the oven to 300 F degrees.
Place brioche slices on a wire rack set on a rimmed baking sheet. Bake the slices for 15 minutes, flipping halfway through the baking process.
Once ready, remove bread from the rack and set it aside to cool.
Turn the heat down to 200 F degrees. Return the baking sheet back into the oven.
Whisk together the milk, egg yolks, brown sugar, melted butter, vanilla extract, cinnamon, and salt in a large – flat Pyrex. I used my 13X9 inch Pyrex.
Soak 1 slice at a time into the milk mixture - 20 seconds long on each side for each slice. It should be wet, not falling apart. Let the excess milk mixture drip off. Place it on a baking sheet lined with parchment paper. Repeat the same process with the rest of the slices.
Heat 1/2 tablespoon of butter in a large (12-inch) non-stick skillet, over medium heat.
Using a slotted spatula, transfer 2 slices of Brioche on to the skillet, and cook for 3-4 minutes on each side or until they turn golden brown. If they turn golden brown too quickly turn down to heat just a little.
Place cooked slices onto the baking sheet in the oven to keep them warm until you are ready to eat.
Repeat the same process for the rest of the Brioche slices using 1/2 tablespoon butter for each time.