Portabella Mushroom Sandwich

This is my latest favorite take on the Portabella Mushroom Burger that exists in many different forms out there. This is simple and delicious. It goes well with salad or a side of steamed veggies.

For each sandwich:

• 1 portabella mushroom cap (stem removed) and wiped clean with a slightly damp towel
• 2-3 thinly sliced rounds of red onion
• 1/2 of a roasted red pepper (jarred are fine--if you have some that a pre sliced or chopped a tbs or two should be enough)
• 1-2 thin slices of smoked Gouda
• balsamic mayonnaise (1 tbs of balsamic vinegar whisked or stirred into 1/4 cup mayonnaise)
• 2 slices of bread, toasted (the mushrooms are so juicy that if you don't toast the bread, it can get mushy)
• 2 tsp of olive oil
• salt and pepper

Assemble all of your ingredients. Heat olive oil in a skillet on medium until shimmering. Place mushroom caps in the skillet, gill/stem side down. Cook without flipping, pressing down on the caps occasionally with a spatula for 4-5 minutes, until starting to brown and juices just start to flow out and into the pan. Flip and cook 3-4 minutes, pressing with the spatula as before until browned, tender and juicy. Remove from heat, and season lightly with salt and pepper.
Spread toasted bread slices with the balsamic mayonnaise. Place onion slices on one side, then the mushroom cap, cheese, roasted red pepper, and other slice of bread.