Prep the bread: Slice the baguette on a slight angle into thick pieces.
Day-old bread works best because it soaks up custard without falling apart.
Make the custard: In a wide bowl, whisk together eggs, milk, granulated sugar, brown sugar, vanilla, cinnamon, and salt until smooth and well combined. You want no streaks of unblended egg.
Soak smart: Place 3–4 slices in the custard at a time. Let them soak for about 20–30 seconds per side if the bread is slightly stale, or up to 1 minute per side if very dry.
The centers should feel heavy but not mushy.
Preheat and stage: Set your oven to 300°F (150°C) and place a baking sheet inside. This will help keep batches warm and finish the center without burning the edges.
Heat the pan: Warm a large skillet or griddle over medium to medium-low heat. Add 1 tablespoon butter and 1/2 tablespoon oil.
The oil helps prevent burning, while butter adds flavor.
Cook the first batch: Lay soaked slices in the hot pan. Cook 2–4 minutes per side until the edges turn deep golden and crisp. Adjust heat if they darken too fast.
Hold in the oven: Transfer finished slices to the warm baking sheet.
This sets the custard inside and keeps everything hot while you cook the rest.
Repeat: Add the remaining butter and oil as needed and continue cooking the rest of the slices, keeping the pace steady so nothing scorches.
Serve: Plate hot with a pat of butter and warm maple syrup. Add berries, a dusting of powdered sugar, or toasted nuts for crunch if you like.