1-First Step: Preheat the oven to 375°F and arrange the rack in the middle. Dice the onion, peel and cut the carrots and celery into 1/2-inch pieces, mince the garlic, and chop the fresh thyme or measure the dried thyme.

2-Second Step: Melt 4 tablespoons of the unsalted butter in a large skillet over medium-high heat. Add the onion, carrots, celery, thyme, 1 1/2 teaspoons kosher salt, and 1/2 teaspoon black pepper. Sauté until the vegetables soften and start to brown, about 5 to 7 minutes.

3-Third Step: Stir in the 1/4 cup all-purpose flour and garlic, and cook until fragrant and no dry spots remain, about 30 seconds to 1 minute.

4-Fourth Step: Gradually pour in the 2 cups low-sodium chicken broth and 1 cup milk, scraping the bottom of the skillet. Bring to a boil, then reduce heat and simmer until the mixture thickens enough to coat the back of a spoon, about 4 to 5 minutes.

5-Fifth Step: Add the 1 pound cooked boneless chicken and 1 cup frozen peas, and mix well. Adjust seasoning with additional kosher salt and black pepper as needed.

6-Sixth Step: Transfer the mixture to a 9×13 baking dish and smooth into an even layer. Separate the biscuits and arrange them evenly on top of the filling.

7-Seventh Step: Bake for 20 to 30 minutes until the biscuits are golden and the filling bubbles in the center. Rotate the dish midway through baking for even cooking, and cover with foil if the biscuits brown too quickly. Melt the remaining 2 tablespoons unsalted butter and brush it over the biscuit tops before serving.