- Spread mustard on each slice of bread. Layer the cheese and arugula on 4 slices of bread. Close the sandwiches.
- In a skillet, melt half the butter. Brown 2 sandwiches at a time for 3 to 4 minutes per side or until the cheese has melted.
You can replace the Ossau-Iraty cheese by goat cheese, cheddar or 8 sliced bocconcini with 60 ml (1/4 cup) of grated Parmesan cheese.