Ingredients:

  • 3 cups cooked chicken, shredded or diced
  • 2 medium leeks, white and light green parts only, thoroughly washed and thinly sliced
  • 2 tablespoons unsalted butter
  • 2 cloves garlic, minced
  • 3 tablespoons all-purpose flour
  • 2 cups low-sodium chicken stock
  • 1 cup whole milk, warmed slightly
  • 1 cup sharp cheddar cheese, grated
  • 1/2 cup Gruyère or Monterey Jack cheese, grated
  • 1 teaspoon Dijon mustard
  • 1 tablespoon fresh parsley, chopped
  • Salt and freshly ground black pepper to taste
  • 1 cup Panko breadcrumbs
  • 3 tablespoons unsalted butter, melted (for topping)
  • 1/4 cup grated Parmesan cheese
  • 1/2 teaspoon dried thyme

Instructions:

  1. Preheat oven to 375°F (190°C). Lightly grease a 9x13 inch casserole/baking dish.
  2. Melt 2 tbsp butter in a large skillet over medium heat. Add sliced leeks and sauté gently for 8–10 minutes until very soft and translucent. Add minced garlic during the final minute.
  3. Sprinkle the flour over the leeks/garlic mixture and cook, stirring constantly, for 1 minute. Gradually whisk in the warm chicken stock until smooth, then slowly whisk in the warm milk. Bring to a gentle simmer, stirring until the sauce thickens enough to coat the back of a spoon (about 5 minutes).
  4. Remove the pan from the heat. Stir in both grated cheeses, Dijon mustard, salt, and pepper until melted and smooth. Fold in the shredded chicken and fresh parsley. Taste and adjust seasoning.
  5. Pour the chicken/leek mixture evenly into the prepared casserole dish.
  6. In a small bowl, mix the Panko breadcrumbs, 3 tbsp melted butter, Parmesan, and dried thyme until evenly coated. Sprinkle evenly over the casserole mixture.
  7. Bake for 20 minutes covered loosely with foil. Remove the foil and bake for another 10–15 minutes until the topping is deep golden brown and the filling is bubbling.
  8. Let the casserole rest for 5–10 minutes before serving.