Directions

1. Heat olive oil in heavy skillet. Add onions; cook over low heat 30 minutes, stirring occasionally, until onions reduce and turn a caramel color.
2. Preheat indoor grill, panini grill or sandwich-maker. Spread 1 teaspoon of the honey mustard on each of 4 bread slices. Top evenly with caramelized onions and 1 slice of Swiss cheese. Top with remaining bread slices.
3. Place sandwiches on grill; cover and cook 4 minutes or until cheese melts. Cool slightly; slice and serve.