Prep the Brioche & Baking Dish: Butter a 9x13-inch ceramic or glass baking dish generously with 1 tablespoon softened butter. Place the cubed brioche bread in the dish, spreading it out into an even layer.

Caramelize the Cinnamon Apples: Melt 3 tablespoons unsalted butter in a large skillet over medium heat. Add sliced apples, dark brown sugar, cinnamon, nutmeg, and apple cider. Sauté for 6 to 8 minutes until apples are tender, fragrant, and coated in a glossy caramel sauce. Remove from heat and gently spoon over and tuck between the brioche cubes in the baking dish.

Whisk the Custard: In a large mixing bowl, whisk together the eggs, whole milk, heavy cream, maple syrup, vanilla extract, cinnamon, cardamom, and sea salt until completely smooth and emulsified.

Soak Casserole (Overnight): Slowly pour the custard evenly over the entire dish, ensuring every cube of brioche is coated. Gently press down on the bread with the back of a spatula so it absorbs the custard. Cover tightly with plastic wrap or foil and refrigerate overnight (at least 6 hours, up to 18 hours).

Mix Crisp Pecan Streusel: In a small bowl, mix flour, brown sugar, cinnamon, and chopped pecans. Cut in the cold cubed butter using a pastry blender or your fingertips until crumbly pea-sized clusters form. Keep refrigerated until ready to bake.

Bake to Golden Puffed Perfection: In the morning, remove casserole from refrigerator 20 minutes prior to baking to take off the chill. Preheat oven to 350°F (175°C). Uncover casserole and scatter the pecan streusel evenly over top. Bake uncovered for 45 to 50 minutes until the top is deeply golden brown, edges are crisp, and center is set (a knife inserted into center comes out clean).

Rest, Dust & Serve Warm: Let casserole rest for 10 minutes so custard fully sets into sliceable portions. Dust generously with confectioners powdered sugar, slice into squares, and serve warm with a generous drizzle of warm pure maple syrup!