Spread 2 tablespoons of peanut butter evenly onto two slices of bread. Place the remaining slices on top to create two sandwiches.

In a shallow dish, whisk together eggs, milk, sugar, vanilla extract, and ground cinnamon until well combined.

Place a large skillet or griddle over medium heat and add the butter, swirling to coat the surface once melted.

Submerge each sandwich into the custard mixture for approximately 20 seconds per side, ensuring the bread is thoroughly soaked.

Transfer the sandwiches to the hot skillet and cook for 3 to 4 minutes per side until the exterior is golden brown and the peanut butter center is warmed.

Remove from the heat and slice diagonally before serving.