Preheat the oven to 300°F (150°C) and place a baking sheet inside to keep cooked French toast warm.
In a shallow dish, whisk together 6 large eggs, 1/2 cup half-and-half (or cream or whole milk), 1/4 cup pure maple syrup, 1 teaspoon ground cinnamon, 1 teaspoon vanilla extract, and a dash of salt until well combined.
Heat a large non-stick skillet over medium heat and add 1 tablespoon unsalted butter; let it melt and coat the pan.
Working one slice at a time, dip a slice of bread into the egg custard, coating both sides and letting excess drip off.
Place the coated bread in the hot skillet and cook until browned, about 2–3 minutes per side, adding more butter to the pan as needed.
Transfer cooked slices in a single layer to the preheated baking sheet to keep warm and finish cooking the remaining slices the same way.
Once all slices are pan-fried, bake them on the baking sheet in the oven for 10 minutes to finish cooking through.
Serve warm with additional maple syrup, butter, or berries as desired.