Cut bread into 1-inch-thick slices. Trim crusts; cut bread into 1-inch cubes. In a bowl, beat eggs, milk, vanilla, and cinnamon. Add 2 cups bread cubes and mix to saturate.
Lightly butter a 10- to 12-inch nonstick frying pan. Place pan over medium-high heat. Lift bread cubes from mixture, shaking off excess liquid. Add cubes to hot pan and cook (adjust heat if necessary), turning as needed, until golden brown, about 5 minutes. Keep warm.
Repeat to soak and cook remaining cubes. Discard any remaining egg mixture.