Set a medium skillet over medium high heat. Coat with olive oil. Add sliced mushrooms, garlic, and vegetables. If using tomatoes, wait until the mushrooms are cooked, turn off the heat, and fold them in. Sauté until mushrooms are browned and vegetables are tender, but not overcooked and too shrunken, about 2-3 minutes. Mine took 2 ½ minutes.

Transfer this mushroom mixture to a plate. Using a paper towel, carefully wipe down the surface of the skillet for reuse.

Coat the skillet with oil and set over medium high heat. Place a tortilla onto the skillet and sprinkle with ¼ cup of the cheese, ½ the mushroom mixture (leaving behind any excess juices), and a sprinkle of salt to taste.

Heat until the cheese starts melting, then place another tortilla on top. Press down until the top tortilla sticks to the cheese. Brush or drizzle the un-crisped tortilla with oil, then flip to crisp the other side of the quesadilla.

Press down with a heatproof spatula to ensure even cooking on all sides. Cook until evenly golden on both sides. I like to flip the quesadilla and crisp it on both sides multiple times for extra crispiness. Repeat for the next mushroom quesadilla.

Slice each quesadilla into 6-8 pieces, then serve with Baked Tortilla Chips, guacamole and Pineapple Salsa or this delicious Black Bean and Corn Salsa.