Whisk together the milk and eggs in a wide shallow bowl.
Dip the brioche slices into the egg and milk mixture for one minute, making sure the liquid soaks into the brioche on both sides.
Heat a knob of butter in a large, non-stick frying pan over a medium-high heat. Once the butter is melted, fry the brioche slices for two minutes on each side until golden-brown and crisp. Remove from the pan and place onto a serving plate.
Combine the caster sugar and cinnamon in a small bowl and set aside.
Add another knob of butter to the pan over a high heat. Once melted, add the sliced banana to the pan, toss in the melted butter and fry for two minutes, or until caramelised lightly on the outside.
Serve the French toast with the caramelised banana, a sprinkle of the cinnamon sugar (any extra can be stored and used again) and a drizzle of maple syrup.