Cut bread into 8 large wedges. Whisk the eggs, buttermilk, cream, granulated sugar, vanilla, and cinnamon in a large baking dish. Add the bread and turn occasionally until soaked through, about 15 minutes. Preheat oven to 250.

Put the confectioners' sugar in a fine-mesh sieve. Melt 1 tbsp of butter in a large nonstick skillet over medium heat. Add half of the bread and dust generously with the confectioners' sugar; cook, turning and dusting often with more confectioners' sugar until golden brown and carmelized, 10-12 minutes (add more butter to skillet if needed.)

Transfer the French toast to a baking sheet and keep warm in the oven. Add 1 more tbsp butter to the skillet and repeat with remaining bread. Serve with maple syrup.