Add the pepperoni and mushrooms to a large nonstick skillet over medium-high heat. Cook until the mushrooms develop some color and begin to shrink, about 6-8 minutes. Stir occasionally to avoid burning.

Add the sun dried tomatoes and stir everything together in the skillet before transferring to a bowl. Set aside.

Reduce the heat to medium-low and place a tortilla in the skillet. Top one half of the tortilla with 1/2 oz (14g) of shredded mozzarella, 45g (about 3 Tbsp) of the pepperoni filling, and another 14g of mozzarella on top.

Fold the empty half of the tortilla over and briefly press to melt the cheese. Continue cooking until golden brown on both sides. Repeat to finish all 6 quesadillas. Once you get comfortable, you can get 2 quesadillas going in the skillet at the same time.

Slice each quesadilla into 3 triangles and serve with marinara or your choice of dipping sauce.