Preheat a griddle to 325°F. Crack eggs into a large bowl. Add flour, cinnamon, and nutmeg. Whisk into a smooth paste. Add brown sugar, milk and vanilla, whisk to combine. Dip bread slices into batter coating both sides. Place onto griddle (greased) and cook on each side until golden on each side. Cool any unused toast on a cooling rack to cool and place in a freezer bag with wax paper between each slice.