Ingredients:
- 4 cups cooked, shredded chicken (rotisserie is recommended)
- 4 tablespoons unsalted butter
- 1 medium yellow onion, finely diced
- 2 medium celery stalks, finely diced
- 1/4 cup all-purpose flour
- 2 cups low sodium chicken broth
- 1 cup heavy cream
- 1 teaspoon dried thyme
- 1 teaspoon salt (or to taste)
- 1/2 teaspoon black pepper (or to taste)
- 2 tablespoons fresh parsley, chopped
- 1 cup frozen peas and carrots mix
- 1/2 cup frozen corn
- 1 cup all-purpose flour (for topping)
- 1/2 cup old-fashioned rolled oats
- 1/4 cup packed brown sugar
- 1 teaspoon garlic powder
- 1/2 teaspoon salt (for topping)
- 1/2 cup (1 stick) cold unsalted butter, cubed (for topping)
Instructions:
- Preheat the oven to 375°F (190°C). Lightly grease a 9x13 inch baking dish.
- Melt 4 tablespoons of butter in a large skillet over medium heat. Add the diced onion and celery and cook until softened, about 5–7 minutes.
- Whisk in 1/4 cup of all-purpose flour to the vegetables, cooking for 1 minute until a pale paste (roux base) forms.
- Gradually whisk in the chicken broth until smooth. Bring to a gentle simmer, then stir in the heavy cream, dried thyme, 1 tsp salt, and 1/2 tsp pepper. Cook until the sauce thickens enough to coat the back of a spoon (about 5 minutes).
- Remove the sauce from the heat. Stir in the shredded chicken, frozen peas and carrots, and frozen corn until everything is evenly coated. Taste and adjust seasoning.
- Pour the entire chicken mixture evenly into the prepared baking dish.
- Prepare the topping: In a separate bowl, combine 1 cup flour, rolled oats, brown sugar, garlic powder, and 1/2 tsp salt. Cut in the cold, cubed butter using your fingertips or a pastry blender until the mixture resembles coarse, wet sand.
- Sprinkle the topping evenly over the chicken mixture. Bake for 30–35 minutes, or until the filling is bubbly and the topping is deep golden brown and crisp.
- Allow the casserole to rest for 10 minutes after removing it from the oven. Garnish with fresh parsley before serving.