Spread 1 tablespoon of nutella on each slice of bread. Spray the other side with cooking spray.
Sprinkle some toasted coconut onto each slice of bread.
Spread the sliced bananas onto two slices of bread in a single layer. Alternatively, you can mash the bananas first and spread the mixture evenly on two slices of bread. The sandwiches will taste the same whether you mash the bananas or not. It’s just a matter of texture. Cover the bananas with the other slice of bread.
Heat a grill pan or a panini press. When the pan is hot, place a sandwich on top. Grill each side for about 2 minutes, or until you see nice grill marks on the bread. Repeat for the other sandwich.
Cut the sandwiches in half and serve. Best served warm.