Preheat the oven to 325°F/160°C, fit a sheet pan with a wire rack and set aside.
In a large bowl, whisk together the eggs, half and half, vanilla, cinnamon, nutmeg, brown sugar, and salt. That’s the custard.
Pour the custard into a pie plate, or any casserole dish that fits 2-4 toasts at once.
Preheat a 12-inch skillet over medium-low heat, and melt the butter.
Dip the toasts in the custard mixture, flipping after 20 seconds per side, allow any excess to drip into the dish and immediately transfer to the hot skillet.
Cook in the hot skillet for 3-5 minutes per side or until golden brown, puffed and crisp. Transfer to the sheet pan fitted with a wire rack, and allow the custard to set in the oven before serving.