Chicken Pot Pie Crumble

1 ½ lbs. chicken, cooked and cut up (2-3ish cups)
1 can chicken broth
2 Tb vegetable oil
1 onion, chopped fine (about 1 cup)
3-4 carrots, peeled and sliced (about 1 cup)
½ c. celery chopped fine
Salt and pepper (to taste)
4 Tb. (1/2 stick) unsalted butter
½ c. flour
1 c. milk
¾ c. frozen peas

Crumble topping:
2 c. flour
2 tsp. baking powder
¾ tsp. salt
½ tsp. pepper
1/8 tsp. cayenne pepper
6 Tb. unsalted butter (cut into ½ inch cubes and chilled)
¾ c. Parmesan cheese (REAL)
1 c. heavy whipping cream

For the topping:
Combine flour, baking powder, salt, pepper, and cayenne in large bowl. Sprinkle butter pieces over top of flour. Using fingers, rub butter into flour mixture until it resembles coarse cornmeal. Stir in Parmesan.  Add cream and stir until just combined. Crumble mixture into irregularly shaped pieces onto a baking sheet. Bake at 450 until fragrant and starting to brown (10-13 min). Set aside.

For the Filling:
Heat 1 Tb oil in pot over medium heat. Add onion, carrots, celery, salt and pepper. Cover and cook till just tender(about 5 minutes). Mix chicken in with veggies and set aside. Heat butter in same pot. When foaming stops, stir in flour and cook for 1 minutes. Slowly whisk 1 can chicken broth and milk. Bring to simmer and stir till sauce thickens about 1 minutes. Add S&P to taste. Remove from heat, stir in veggie/chicken mixture and peas into sauce.

Pour mixture into 9x13 pan. Scatter crumble topping evenly over filling. Bake at 400 till filling is bubbling and topping is well browned (12-15 minutes) Serve hot.