Heat an electric griddle to 300°F, or heat a stovetop griddle or skillet over medium heat.
In a large measuring cup, whisk the eggs until smooth and no stringy bits remain. Add the milk, vanilla, and cinnamon, and whisk until well combined. Pour the mixture into a wide, shallow dish, such as a small casserole dish.
Dip each slice of banana bread into the egg mixture one at a time. Quickly turn to coat both sides, but do not let the slices soak.
Lightly butter the griddle, then place the coated slice onto the surface. Cook for about 3 minutes per side, or until golden brown, adjusting the heat as needed so the outside browns without burning. Repeat, buttering the griddle as needed before adding additional slices.
Transfer cooked slices to a 200°F oven to keep warm while you finish the remaining pieces.
Top with sliced bananas and chopped nuts. Serve with your favorite syrup.