Prep the bread: If your brioche is very fresh and soft, lay the slices on a sheet pan and pop them into a 200°F (95°C) oven for 8 to 10 minutes to dry them out slightly. Not toasted, just a touch firmer. This helps them drink up the custard without falling apart.
Make the custard: In a large bowl, whisk the eggs, egg yolks, sugar, vanilla, and salt until smooth. Whisk in the heavy cream and milk. If you’re using zest or nutmeg, add it now. The mix should smell like vanilla custard—because it is.
Soak the bread: Pour the custard into a shallow dish. Add the brioche in a single layer. Let it sit for 2 to 3 minutes, then flip and soak the other side for another 2 to 3 minutes, until the slices feel heavy and evenly saturated but not falling apart. If you prefer a deeper soak (more pudding-like centers), go 5 minutes per side.
Cook the toast: Heat a large nonstick or seasoned cast-iron skillet over medium-low. Add a little butter to coat the surface. Cook the soaked slices in batches for about 3 to 4 minutes per side, until golden and set in the center. Adjust the heat if browning too quickly. Slide finished slices onto a wire rack set over a sheet pan and keep warm in a 300°F (150°C) oven while you cook the rest.
Brûlée the tops: Sprinkle about 1 to 1 1/2 teaspoons sugar evenly over each slice. For a torch, hold the flame a few inches away and move it in circles until the sugar melts, bubbles, and turns amber. For a broiler, place the sugared slices on a foil-lined pan and broil on the top rack for 30 to 90 seconds, watching like a hawk. Pull them the moment the sugar is glassy and browned.
Rest, then serve: Give the toast 1 minute to let the sugar harden. Tap gently with a spoon. Hear that little crack? That’s the magic. Serve with berries and a touch of maple or whipped cream if you like. A sprinkle of flaky salt makes the caramel pop.