Preheat oven to 400°F (200°C). Grease a 9x13-inch ceramic baking dish (or use an oven-safe deep cast iron skillet).

In a large Dutch oven or skillet over medium heat, melt 4 tablespoons of butter. Add diced onion, carrots, and celery. Sauté for 6 to 8 minutes until vegetables begin to soften.

Add minced garlic, fresh thyme, salt, and pepper; sauté for 1 minute until fragrant. Sprinkle flour over the vegetables and stir constantly for 2 minutes to cook out raw flour taste.

Slowly whisk in chicken bone broth and heavy cream, whisking constantly to prevent lumps. Bring to a gentle simmer for 4 to 5 minutes until sauce thickens into a glossy velouté.

Remove from heat and fold in the shredded chicken and frozen sweet peas. Pour the filling into the prepared baking dish.

Prepare the biscuit dough: In a medium bowl, stir together biscuit mix, shredded cheddar cheese, minced parsley, and garlic powder. Add buttermilk and 2 tablespoons melted butter, stirring just until a soft, moist drop dough forms.

Using a large cookie scoop or spoon, drop 6 to 8 generous mounds of biscuit dough evenly across the top of the hot chicken filling.

Brush the biscuit tops with the remaining 2 tablespoons melted butter.

Bake uncovered for 22 to 26 minutes until the biscuits are golden brown, cooked through in the center, and the creamy filling is bubbling around the edges.

Let rest for 10 minutes before scooping into bowls to allow sauce to settle. Serve hot!