1 tbsp (15 mL) each butter and olive oil
4 ciabatta buns
1 lb (500 g) Mortadella Bologna PGI, sliced
½ lb (250 g) sliced fontina, preferably PDO
- Cut each onion in half lengthwise, slicing through root end. Place onions, cut-side down, on a cutting board, then thinly slice into semicircles.
- Heat butter and oil in a medium-sized frying pan over medium-low heat. Add onions, then sprinkle with salt. Cook, stirring often, until caramelized, about 30 minutes.
- Slice buns in half. Layer bottom halves with caramelized onions, mortadella and fontina. Sandwich with tops. Delicious served with fresh mixed greens.