Melt 3 tablespoons unsalted butter in a medium skillet over medium heat. Add 1/2 cup packed brown sugar and 2 tablespoons maple syrup; stir until sugar dissolves and mixture is bubbling lightly.

Stir in 1/2 teaspoon ground cinnamon and 2 tablespoons apple cider (or water) to deglaze. Add the sliced apples and cook, stirring occasionally, until apples are just tender and coated in a glossy caramel, about 5–7 minutes. Remove from heat and let cool slightly.

Custard & Soaking

Preheat oven to 375°F (190°C). Grease a 9x13-inch baking dish with 1 tablespoon unsalted butter.

In a large mixing bowl or shallow dish, whisk together 4 large eggs, 1 cup whole milk, 1/2 cup heavy cream, 1 teaspoon vanilla extract, 1 teaspoon ground cinnamon, 1/4 teaspoon ground nutmeg, 2 tablespoons granulated sugar, and 1/4 teaspoon fine sea salt until smooth and slightly frothy.

Arrange 6 slices of thick-cut bread in a single layer in the prepared baking dish. Spoon about half of the warm caramelized apple mixture evenly over the bread, pushing slices into crevices so apples settle between and on top of the bread slices.

Pour the custard mixture evenly over the bread and apples, pressing gently on slices so bread soaks up custard. Let sit at room temperature for 10–15 minutes to absorb (or cover and refrigerate up to 1 hour for deeper soak). If any custard remains in the bowl, pour it over the top.

Baking & Finish

Place the baking dish in the preheated oven and bake for 25–30 minutes, until custard is set in the center and the top is golden. If the top is browning too quickly, tent loosely with foil for the last 5–10 minutes.

Remove from oven and let rest for 5–10 minutes. Dust the top with 1 tablespoon powdered sugar and scatter 1/4 cup toasted chopped pecans or walnuts if using. Serve warm with pure maple syrup to taste.