- 2 tablespoons butter
- 1 large yellow onion
- 1/4 teaspoon sea salt
- 4 slices multi-grain bread
- 1 tablespoon butter
- 2–3 tablespoons wholegrain mustard
- 3 ounces cheese (white cheddar, havarti, or fontina), thinly sliced
- Bread and Butter Pickles, for serving
- In a large skillet melt 2 tablespoons butter. Cut onion into thin and even slices (a mandoline is great for this). Add onions, making sure heat is on low, cover, and cook until onions are tender and brown, 45-60 minutes. Stir in salt and remove from heat.
- Preheat broiler. Butter each slice of bread and place on a sheet tray. Bake the bread under the broiler, flipping once, until just starting to crisp. Keep an eye on the toast- this will happen quickly.
- Remove bread from oven and smear on 2-3 teaspoons of mustard. Divide the caramelized onion over the toast and top with cheese slices. Place back under the broiler and cook until cheese is melting and bubbly, 60-90 seconds (again, goes fast- keep an eye on it!) Serve toast with sweet pickles.