Spread each of the 4 slices of Texas toast with about 2 tablespoons chocolate peanut butter (about 8 tablespoons total), dividing it evenly.
Arrange the banana slices in a single, even layer on top of two of the peanut-buttered slices.
Top each banana-topped slice with one of the remaining peanut-buttered slices, peanut-butter sides facing the bananas, to make 2 sandwiches; press gently to seal and set the sandwiches aside.
In a medium bowl whisk together the 2 eggs, 1/4 cup milk, 1 tablespoon granulated sugar, and 1/2 teaspoon cinnamon until combined.
Heat a large skillet over medium heat and add about 2 tablespoons unsalted butter. Let the butter melt and coat the skillet.
Working one sandwich at a time, dip the sandwich into the egg mixture, coating both sides; allow any excess custard to drip off, then place the sandwich in the hot skillet.
Cook each sandwich about 3 to 4 minutes per side, flipping once, until both sides are lightly golden brown and cooked through.
Transfer to a cutting board, slice if desired, and serve immediately while warm.