In a wide shallow bowl or container, whisk together eggs, milk, vanilla, cinnamon, nutmeg and kosher salt.
Preheat a griddle over medium heat and melt the tablespoon butter. Soak each side of 4 slices of bread in the egg mixture about 30 seconds per side until it becomes saturated. Place the bread on the hot skillet and cook 2 to 3 minutes per side, until browned.
Serve immediately with maple syrup. Leftovers last refrigerated up to 3 days.