Preheat the oven to 375°F. Grease a 9 x 13-inch baking pan with nonstick spray and set aside.

In a large frying pan over medium heat, melt the 2 tablespoons of butter. Add the 2 thinly sliced small onions and cook, stirring frequently, until the onions are softened and beginning to brown (about 8–10 minutes).

Add the 1–2 minced garlic cloves to the pan and cook, stirring, until fragrant (about 30–60 seconds).

Remove the pan from the heat. Add the 2 cups chopped cooked chicken, ½ cup chopped jarred roasted red peppers (reserve a small amount to use as garnish), and the 6 ounces cream cheese (in cubes). Return the pan to very low heat and gently stir until the cream cheese has melted and the mixture is smooth and combined.

If you want cheese in the filling, stir in the optional 4 ounces shredded Monterey Jack now until melted and evenly incorporated. Taste the filling and add salt if desired. If you want additional dried herbs or garlic powder, add them now.

Pour a thin layer of the green enchilada sauce into the bottom of the prepared baking pan.

Spoon about 1/3 cup of the filling down the center of each flour tortilla. If you did not add the optional 4 ounces of cheese to the filling, you may sprinkle a little of the 8 ounces shredded Monterey Jack into each tortilla before rolling, if desired.

Roll each tortilla and place seam-side down in the prepared pan. Continue until all tortillas are filled and arranged in the pan.

Pour the remaining green enchilada sauce evenly over the rolled enchiladas. Sprinkle the 8 ounces shredded Monterey Jack evenly over the top.

Garnish with the reserved roasted red peppers, if desired.

Bake uncovered at 375°F for 20 minutes, until the sauce is bubbly and the cheese is melted. Let the pan sit a few minutes before serving.