Makes 4 sandwiches
On a clean work surface, lay out 4 slices bread. Spread butter on each piece. Flip over 4 pieces bread and spread 2 tablespoons peanut butter on them. Place 2 ounces chocolate on top of peanut butter, then arrange banana slices on top of chocolate. Top each with a remaining slice of buttered bread. Place 2 sandwiches at a time in a panini maker or grill pan over medium heat (if using a grill pan, top with a sandwich press or heavy plate) and cook for 3 minutes or just until chocolate has melted. Repeat with 2 remaining sandwiches. (Alternate cooking method: Heat 1 tablespoon butter in a saute pan; when hot and bubbly, add 2 sandwiches to pan. Cook for 2 minutes per side or until bread is golden brown and chocolate has melted. Repeat with remaining sandwiches.)
Slice sandwiches in half or in quarters and serve immediately.
The sandwiches can be made with a variety of ingredients. For example, replace the chocolate with 1 tablespoon of honey or add cherry or plum jam instead of the bananas and chocolate. Almond butter can be substituted anywhere peanut butter or other nut butters are used.