Preheat your oven to 400°F (200°C).

Melt the butter in a large 10 or 12-inch cast-iron skillet over medium-high heat. Add the diced onion, carrots, and celery, sautéing for 5-7 minutes until the vegetables soften.

Sprinkle the flour over the vegetables and stir constantly for 1 minute to cook off the raw flour taste.

Gradually pour in the chicken broth, whisking constantly to ensure no lumps form. Bring to a gentle simmer, then stir in the heavy cream. Let it bubble and thicken for 3-4 minutes.

Fold in the cooked chicken, frozen peas, fresh thyme, salt, and pepper. Taste and adjust seasoning as necessary. Remove from heat.

Open the tube of biscuits and arrange them in an even layer directly over the top of the hot chicken filling in the skillet.

Transfer the skillet to the preheated oven and bake for 12-15 minutes, or until the biscuits are deep golden brown and cooked through.

Let the pot pie cool for 5 minutes before serving directly from the skillet.