Portobello Mushroom Burgers - Slender Kitchen

Ingredients

• 4 portabella mushroom caps
• 2 tbsp balsamic vinegar
• 1 tbsp olive oil
• 1 tbsp Worcestershire sauce (vegan if needed)
• 1 tbsp Italian seasoning
• 1 1/2 tsp Montreal steak seasoning
• 1 red onion, sliced
• 4 slices low fat Swiss cheese (like Jarlsberg)
• 1 tomato, sliced
• 1 avocado, sliced
• 2 cups arugula
• 4 reduced calorie hamburger buns