Step 1

Preheat oven to 375 degrees and grease a 3-quart casserole dish.

Step 2

Melt the butter in a large skillet with high sides or a Dutch oven. Add onion and celery and cook until soft, about 6 to 8 minutes. Add garlic and cook 1 more minute. Season with salt and pepper.

Step 3

Sprinkle the 1/2 cup flour over onion and celery and stir for 1-2 minutes.

Step 4

Gradually whisk in chicken broth and then heavy cream. Bring to a boil and add peas and carrots, chicken and thyme.

Step 5

Simmer until thickened. Season to taste with salt and pepper. Pour into prepared casserole dish.

Step 6

To make biscuit topping, stir together flour, baking powder, baking soda, and salt. Cut the butter into the flour mixture using your hands until there are no pieces bigger than a small pea. Stir in buttermilk just until combined. You may not need all of it. You just need enough for all of the flour to be incorporated.

Step 7

Drop biscuit dough evenly over top of casserole. Drizzle with melted butter and sprinkle with Parmesan.

Step 8

Bake for 30 to 35 minutes.