Step 1:
Grease a 9×13-inch baking dish with a little butter or cooking spray. Set it aside while you prep the bread. This will ensure your casserole releases easily and develops a nice golden crust on the bottom.

Step 2:
Cut the brioche into slices about ¾-inch thick. If the loaf is pre-sliced, that’s fine too. Day-old bread works best here—it soaks up the custard beautifully without falling apart. If using fresh bread, you can lightly toast it in the oven for 5 minutes to dry it out.

Step 3:
Spread a thin layer of your chosen jam on one side of half the brioche slices. Think of it like making little open-faced jam sandwiches. Then top each with a plain slice to create a sandwich effect. This layering gives you a jammy surprise in the middle of the casserole.

Step 4:
Arrange the jam sandwiches in the greased baking dish. You can lay them flat, overlap them slightly in a row, or stand them upright like a bread pudding. There’s no wrong way—it’s all about the final look you want.

Step 5:
In a large mixing bowl, whisk together the eggs, milk, heavy cream, sugar, vanilla extract, cinnamon (if using), and salt. Whisk until fully combined and slightly frothy—this will be your custard base.

Step 6:
Slowly pour the custard mixture over the arranged brioche sandwiches in the dish. Make sure to cover all the bread, especially the tops. Press down lightly with a spatula to help the bread absorb the custard.

Step 7:
Cover the dish tightly with foil or plastic wrap and refrigerate for at least 4 hours, or overnight if possible. This allows the custard to fully soak into the bread for the softest, most flavorful texture.

Step 8:
When ready to bake, preheat your oven to 350°F (175°C). Uncover the casserole, brush the tops of the bread with melted butter for extra color, and place it in the oven.

Step 9:
Bake for 40 to 45 minutes, or until the custard is set and the tops are golden brown. If the top starts browning too quickly, you can tent it loosely with foil during the last 10 minutes.

Step 10:
Remove from the oven and let it cool for 10 minutes before serving. Dust with powdered sugar, garnish with fresh berries or mint if desired, and serve with maple syrup or whipped cream on the side.