1. Heat 1 tablespoon olive oil in a large skillet over medium heat. Add the minced garlic and sauté for about 30 seconds, until fragrant but not browned. This little step always reminds me of the stories my dad told while stirring pots—simple flavors building the base of a good meal.
2. Add the chopped spinach to the skillet. Cook, stirring often, until wilted and bright green, about 2-3 minutes. Remove from heat and let it cool slightly. This helps keep the quesadillas from getting soggy, a lesson I learned the hard way on one busy weeknight.
3. In a bowl, combine the wilted spinach, mozzarella, feta, black pepper, and red pepper flakes if using. Stir gently to mix the ingredients evenly.
4. Wipe the skillet clean and return to medium heat. Lightly brush one side of a tortilla with olive oil and place it oil-side down in the skillet.
5. Sprinkle about half of the cheese and spinach mixture evenly over the tortilla in the skillet, leaving a small border around the edges.
6. Top with another tortilla, oil side up. Cook for 3-4 minutes until the bottom tortilla is golden brown and crispy.
7. Carefully flip the quesadilla with a large spatula. Cook the other side for another 3-4 minutes until golden and the cheese has melted.
8. Transfer the quesadilla to a cutting board. Let it rest for a minute (this helps the cheese set just enough to avoid a molten lava mess) then slice into wedges.
9. Repeat the process with the second quesadilla.

From my experience, the key is medium heat—too high and the outside burns before the cheese melts, too low and you end up with a limp, chewy tortilla. And yes, patience is a virtue here. Letting the quesadilla rest after cooking makes all the difference.