Begin by preheating your oven to 375°F (190°C) so it reaches the proper temperature before the quesadillas go in. While the oven is heating, place a sheet of parchment paper on a baking tray. The parchment paper prevents the tortillas from sticking to the tray and helps the quesadillas crisp evenly without burning.

Place a large skillet on the stove over medium heat and pour in the olive oil. Allow the oil to warm for about 20–30 seconds. Swirl the pan gently so the oil spreads across the bottom, creating a thin layer that helps cook the vegetables evenly.

Add the sliced mushrooms to the heated skillet and spread them out in a single layer if possible. Let them cook undisturbed for a minute so they begin to brown. Then stir occasionally as they continue cooking. Mushrooms release moisture while cooking, so allow the liquid to evaporate while they soften and turn lightly golden. This usually takes about 5 to 6 minutes.

Once the mushrooms are browned, add the minced garlic and fresh spinach to the skillet. Stir everything together so the spinach mixes with the mushrooms. Continue cooking for 2 to 3 minutes, stirring occasionally, until the spinach wilts down and becomes soft. The mixture should look evenly combined and fragrant.

Sprinkle the onion powder, salt, and black pepper over the mushroom and spinach mixture. Stir well so the seasoning distributes evenly throughout the filling. Let it cook for another 30 seconds so the flavors blend together before removing the skillet from the heat.

Lay the tortillas flat on a clean surface such as a cutting board or countertop. Using a butter knife or small spatula, spread a thin layer of cream cheese evenly across the surface of each tortilla. This creamy layer helps hold the filling in place and adds extra richness to the quesadilla.

Spoon the warm mushroom and spinach mixture onto one half of each tortilla. Spread the filling evenly so every bite will contain the savory vegetables. Be careful not to overfill the tortillas so they remain easy to fold and bake.

Sprinkle shredded mozzarella cheese over the mushroom and spinach filling. Try to distribute the cheese evenly so it melts smoothly and binds the ingredients together as the quesadilla bakes.

Carefully fold each tortilla in half so the empty side covers the filling, forming a half-moon quesadilla shape. Press gently along the edges so the filling stays inside and the tortilla holds its shape.

Place the folded quesadillas onto the prepared baking sheet lined with parchment paper. Leave a little space between each one so the hot air in the oven can circulate around them and help them crisp up.

Transfer the baking sheet to the preheated oven and bake the quesadillas for 10 to 12 minutes. As they bake, the tortillas will become lightly golden and slightly crisp, while the cheese inside melts and holds the filling together.

Remove the baking sheet from the oven and allow the quesadillas to rest for about 2 minutes so the melted cheese settles slightly. Place them on a cutting board and use a sharp knife or pizza cutter to slice each quesadilla into wedges. Serve warm for the best texture and flavor.