Step 1

In a food processor or blender, combine the sour cream, cilantro, avocado, lime zest and juice and season with salt and pepper. Process until smooth then taste and adjust seasoning accordingly. Transfer the avocado crema to a bowl, cover tightly with plastic wrap and chill until ready to use.

Step 2

Heat the olive oil in a large skillet over medium-high heat until it begins to shimmer. Add the mushrooms, garlic and onions, and cook, stirring often, until just beginning to brown, about 10 minutes. Stir in the beans, season with salt and pepper and cook until warmed through, about 1 minute. Transfer the vegetables to a bowl and keep warm. Wipe the skillet clean with paper towels.

Step 3

Return the skillet to medium-low heat. Place one tortilla on the dry skillet and cook for about 20 seconds per side to make it pliable. Sprinkle ¼ cup cheese onto one half of the tortilla. Top with about one-quarter of the mushroom-bean mixture and then sprinkle with another ¼ cup of cheese.

Step 4

Fold the tortilla over to create a half-moon and cook the quesadilla until the cheese is melted through and the tortilla is golden brown and crisp on both sides, 1 to 2 minutes per side. Transfer the quesadilla to a cutting board, tent with foil to keep warm, and repeat with the remaining tortillas, cheese and mushroom-bean mixture to make three more quesadillas.

Step 5

Slice each quesadilla into quarters and transfer to a serving plate. Serve with the avocado crema on the side.