Start by preheating oven to 425 degrees and move baking rack to top position. Wash and dry all produce. Trim, peel, and finely dice carrots and celery. Halve, peel, and dice half the onion. Peel and mince garlic. Strip half the thyme leaves from stems; mince leaves.
Heat a drizzle of oil in pan and add carrots, celery, and diced onion; season with salt and pepper. Cook, stirring, until veggies are softened, 5-7 minutes. Add garlic and most of the minced thyme; cook until fragrant, 30 seconds.
Add 3 tablespoons butter to pan with veggies. Once melted, stir in flour; cook for 1 minute. • Pour in chicken broth, milk, seasoning, (stock concentrate if using) salt, and pepper. Bring to a boil and cook until thickened, 3-5 minutes. Turn off heat. • Stir in sour cream, peas and soy sauce, then stir in chicken. Season with salt and pepper and a small squeeze of lemon.
Place 1 tablespoon butter in a small microwave-safe bowl; microwave until melted, 30 seconds. • Remove canned biscuits from package • Evenly top filling with biscuits, then brush with melted butter and sprinkle with reserved minced thyme. • Bake on top rack until biscuits are golden brown and chicken is cooked through, 12-15 minutes.
Let pot pie sit for 5-10 minutes to set up and serve.