In a bowl, mix well the eggs, milk, flour, sugar, vanilla, salt, and cinnamon (if used).
Heat a frying pan, add 1 tablespoon of butter, and reduce heat to low.
Dip each slice of bread in the egg mixture for about 20 seconds.
Transfer to the frying pan. Cook on both sides until well browned.
Add extra butter to the frying pan as needed.
Repeat with all the bread slices.
Serve warm with a sweetener: icing sugar, maple syrup, or honey.