Ingredients

• 1 tbsp olive oil
• 3 medium onions, sliced thinly (about 3 1/2 cups)
• 1/2 900-mL carton low-sodium beef broth
• 1 thyme sprig
• 1/4 cup dry sherry (optional)
• 4 tsp Dijon mustard
• 8 slices rye bread
• 4 slices gruyère or swiss cheese, about 120 g

Directions

1. Heat a large non-stick frying pan over high. Add 1 tsp oil, then onions, broth and thyme. Cook, uncovered, stirring often, until liquid is reduced, about 15 min. Add sherry and continue cooking until absorbed, about 5 more min. Remove thyme.
2. Spread Dijon on 4 slices of bread. Top each slice with about 1/3 cup onion mixture and 1 cheese slice. Top with remaining bread.
3. Wipe pan clean. Heat over medium. Brush pan with 1 tsp oil. Cook 2 sandwiches at a time, about 2 min per side. Repeat with remaining oil and sandwiches.