In a medium bowl, combine the shredded or diced chicken, Greek yogurt, and ranch seasoning mix. Mix thoroughly until all the chicken is evenly coated. If adding bacon or scallions, stir them in now. Taste and adjust seasoning.

Place a large non-stick skillet or griddle over medium-high heat. Add half a tablespoon of butter (or oil) to melt and heat the pan.

Lay one tortilla on a flat surface. Sprinkle about 1/4 cup of the cheese blend on one half of the tortilla. Spoon approximately 3/4 cup of the chicken filling evenly over the cheese, leaving a small border.

Sprinkle another 1/4 cup of the cheese blend over the chicken filling.

Fold the empty half of the tortilla over the filling, pressing gently. Place the quesadilla in the hot skillet. Cook for 3-4 minutes until the bottom is golden and crispy, then carefully flip and cook another 3-4 minutes until both sides are crisp and cheese is melted.

Transfer to a cutting board and let rest for 1 minute. Slice into triangles. Repeat with remaining ingredients, adding more butter to the pan as needed. Serve hot.