In a frying pan, melt 3 tablespoons of the butter. Make sure butter does not burn. In a small bowl mix together the peanut butter, honey, and cinnamon. Slice the bananas into 1/4-inch thick slices. Spread the peanut butter mixture on 4 slices of bread and cover with banana slices. Top with the remaining 4 slices of bread. Spread the remaining butter on both sides of the sandwiches. Grill the sandwiches in the frying pan until each side is golden brown.
For topping, combine the sugar and cinnamon in shallow plate. Coat the grilled sandwiches with the mixture. Cut diagonally and serve hot.