1) Preheat an oven to 90C or your oven's lowest setting, and place a rack on a baking sheet.
2) Whisk the milk and eggs in a glass pie or casserole dish until evenly combined.
3) Whisk the sugar and cinnamon in a small bowl.
4) Heat a large skillet over medium heat. Add 10g of butter to the skillet, swirling the pan to coat the surface. Dip 2 slices of bread into the egg mixture and immediately lay in the skillet. Sprinkle the cinnamon sugar on top and cook until the undersides are brown and crisp, about 4 mins. Add a nut-sized bit of butter to the skillet, as needed, and flip the toast, cook until golden on the underside, about 3 mins more.
5) Serve immediately or transfer to the rack in the oven to keep warm. Repeat with the remaining bread and batter. Serve with jam or maple syrup.