Lightly grease the inside of your slow cooker with butter or a bit of cooking spray. If you want to make cleanup a breeze (and who doesn’t?), line it with parchment paper.
Cut your brioche into bite-sized cubes, about 1–2 inches. Slightly stale bread actually works best—it soaks up the custard without turning soggy.
In a large mixing bowl, whisk together the eggs, milk, cinnamon, vanilla, and sea salt until everything is smooth and well combined.
Add the bread cubes to the slow cooker, then pour the custard evenly over them. Gently press down so all the bread gets coated—no dry corners left behind.
Drizzle maple syrup over the top. You can leave it on the surface for a caramelized finish or stir it in slightly for a more even sweetness.
Cover and cook on LOW for 2 to 3 hours, or until the center is set and the edges are just a little golden. The smell at this point? Heavenly.
Scoop into bowls while warm and drizzle with extra maple syrup, a dusting of powdered sugar, or a handful of berries for a pop of color.