Chicken and Filling:
- 1 1/2 pounds chicken
- 2 cups low-sodium chicken broth
- 1 tablespoon olive oil
- 1 onion, chopped fine (about 1 c)
- 3-4 carrots, peeled and sliced (about 1 c)
- 2-3 stalks celery, chopped (about ½ c)
- 1/2 teaspoon salt
- 1/2 teaspoon pepper
- 4 tablespoons butter (1/2 stick)
- 1/2 cup all-purpose flour
- 1 cup milk
- 3/4 cup frozen peas
- 2 cups all-purpose flour
- 2 teaspoons baking powder
- 3/4 teaspoon salt
- 1/2 teaspoon pepper
- pinch of cayenne pepper
- 6 tablespoons butter, cut into 1/2-inch cubes and chilled
- 3/4 cup Parmesan cheese
- 1 cup heavy cream
- Stovetop: Place the chicken and 2 cups broth in a large pot or Dutch oven and bring it to a simmer over medium heat.
- Cook the chicken until it is just done (don’t overcook or it will dry out) – about 10-12 minutes.
- If the chicken pieces are large, you may need to pound them or cut them in half so they will cook more quickly.
- Slow Cooker: Or you can place the chicken and broth in a slow cooker and cook on high for 3 hours or low for 5 hours.
- Transfer the cooked chicken to a medium bowl.
- Pour the broth through a fine-mesh strainer into a liquid measuring cup and reserve.
- Return the pot to the stovetop (no need to wash it).
- Preheat the oven to 400 degrees.
- In a large bowl, combine the flour, baking powder, salt, pepper, and cayenne.
- Sprinkle the chilled butter pieces over the top of the flour.
- Using a pastry cutter, cut the butter into the flour mixture until it resembles coarse crumbs.
- Stir in the Parmesan cheese.
- Add the cream and stir until just combined.
- Crumble the mixture into irregularly shaped pieces onto a baking sheet lined with parchment paper or a silicone baking mat.
- Bake the crumble topping until fragrant and starting to brown, about 15 minutes, tossing halfway through.
- Set aside.
- Meanwhile, heat the olive oil in the now-empty pot over medium heat.
- Add onion, carrots, and celery.
- Add salt and pepper to taste, if desired.
- Cover and cook, stirring occasionally, until just tender, about 5 minutes.
- While the vegetables are cooking, shred or chop the chicken into small bite-size pieces.
- Transfer the cooked vegetables to the bowl with the chicken; set aside.
- Over medium heat, melt the 4 Tbsp butter in the empty pot.
- Stir in the flour and cook for one minute, stirring constantly.
- Slowly whisk in the reserved chicken broth and milk.
- Bring to a simmer and stir occasionally until the sauce thickens, about 5 minutes, taking care not to burn the bottom.
- Add 1/2 tsp salt and 1/2 tsp pepper.
- Remove from the heat and stir the chicken, vegetables and peas into the sauce.
- Pour the filling mixture into a 9×13 pan.
- Scatter the crumble topping evenly over the filling.
- Place the 9x13 pan on a rimmed baking sheet and bake at 400 degrees until the topping is well browned, about 15-20 minutes.
- Let the casserole stand for 10 minutes before serving.