Vegetarian Recipe

Prepare vegetables

Clean mushrooms with a damp paper towel and slice them about 1/4" thick. Halve the tomato, remove excess seeds if very watery, and slice into 1/4" rounds. Core and seed the green bell pepper, then cut into thin strips. Peel and thinly slice the onion. Slice the black olives if not already sliced.

Sauté mushrooms, peppers, and onion

Heat 1 tablespoon olive oil in a large skillet over medium-high heat. Add the sliced mushrooms in a single layer and let them brown, stirring occasionally, about 4 minutes. Push mushrooms to one side, add the remaining 1 tablespoon oil and add the sliced onion and bell pepper. Sauté together until the vegetables are softened and lightly caramelized, about 5–6 minutes. Season with 1/2 teaspoon salt, 1/4 teaspoon black pepper, and the dried oregano while cooking.

Combine with tomato and olives

Remove skillet from heat. Add the sliced tomato, sliced olives, balsamic vinegar, and remaining 1/2 teaspoon salt and 1/4 teaspoon black pepper. Gently toss to combine; the residual heat will slightly warm the tomato without making it mushy. Taste and adjust seasoning.

Prepare the mozzarella and basil

Slice or tear the fresh mozzarella into pieces appropriate for sandwiches (about 6 equal pieces). If using basil, tear or stack-and-slice leaves into ribbons. Reserve for assembly. If you prefer the cheese warmed, return the skillet to low heat, add the mozzarella on top of the warm vegetable mixture for 1–2 minutes until it softens slightly, then remove from heat.

Lightly toast the rye bread slices until just golden. If using garlic, cut the clove in half and rub the cut side across the toasted bread for a subtle garlic note. Spread 1/2 teaspoon softened butter or a light drizzle of olive oil on each slice.

On two slices of rye (for open-faced or top of sandwiches), evenly divide the vegetable and olive mixture. Top with mozzarella pieces and scatter basil leaves over the cheese. Place the remaining bread slices on top to form sandwiches.

If you like the mozzarella melted, place assembled sandwiches in a preheated skillet over low heat, cover, and warm 2–3 minutes per side until the cheese softens and the bread is crisp. Alternatively, broil on a tray for 1–2 minutes, watching closely to avoid burning.

Slice sandwiches in half on the diagonal, serve immediately.