Grilled Portobello Sandwich

Ingredients

• 4 portobello mushroom caps
• 0.25 cup olive oil
• 2 tbsp balsamic vinegar
• 2 cloves garlic – minced
• 0.5 tsp dried oregano
• 1 tsp kosher salt
• 0.5 tsp black pepper – freshly ground
• 0.25 cup mayonnaise
• 1 tsp Dijon mustard
• 1 tsp lemon juice – freshly squeezed
• 4 ciabatta rolls – split
• 2 cups arugula – loosely packed
• 1 tomato – sliced
• 0.5 red onion – thinly sliced
• 4 slices provolone cheese

Instructions

1. Wipe the portobello caps clean with a damp towel, remove the stems, and optionally scrape out the dark gills with a spoon to reduce dripping.
2. In a shallow dish, whisk together the olive oil, balsamic vinegar, minced garlic, dried oregano, kosher salt, and black pepper. Place the mushrooms gill-side up, spoon some marinade into each cap, then turn to coat. Marinate 15–30 minutes, turning once.
3. Stir together the mayonnaise, Dijon mustard, and lemon juice until smooth; set aside.
4. Preheat a grill to medium-high heat (about 400–450°F). Clean and oil the grates.
5. Grill the mushrooms gill-side down until well marked, 4–5 minutes. Flip and grill 3–5 minutes more, until tender and juicy when pierced. During the last minute, top each cap with a slice of provolone and close the lid to melt.
6. Toast the split ciabatta rolls cut-side down on the grill until lightly crisp, 1–2 minutes.
7. Spread the lemon-Dijon mayo on the cut sides of the toasted rolls. Layer arugula on the bottoms, add the cheesy mushroom caps, then top with tomato slices and red onion. Close the sandwiches and serve warm.