1. Preheat oven to 450°F.
2. Prepare filling: Heat a large cast-iron or ovenproof nonstick pan over medium-high for 1 minute. Mist with cooking spray. Sauté chicken until no longer pink, 3 minutes.
3. Add onion and carrots. Saute until onion is slightly browned, about 5 minutes. Add peas and saute for another minute or until thawed.
4. Stir in broth and thyme and cook until broth is warmed, about 2 minutes. Sit in 2 tbsp whole-wheat flour and reduce heat to medium. Stir constantly until broth is thickened, about 2 minutes. Season with pepper and turn off heat, but do not remove pan from element.
5. Begin preparing biscuits: Pour milk in a cup, then add vinegar to milk. Let stand for 2 minutes.
6. In a large mixing bowl, blend 2 cups whole-wheat pastry flour, baking powder, baking soda and salt, if desired. Stir in milk-vinegar mixture, a 1/4 cup at a time, add oil, and then add remaining 2 tbsp whole-wheat pastry flour. (The dough will be slightly sticky. If it is too sticky, add another tbsp of flour.)
7. Using your hands, form 12 small biscuits, about 1 1/2 to 2 inches in diameter. (If the biscuits are exceptionally sticky, dust your hands with a little bit of flour to make it easier to form them.) Ladle chicken-vegetable mixture into 4 large ramekins, individual casserole dishes or soup tureens, about 3/4 cup per serving. Place 3 biscuits on top of each ramekin and place all ramekins into a cookie sheet or baking pan lined with aluminum foil. (The biscuits will bake on top of chicken-vegetable mixture.) Place pan on rack in middle of oven. Bake for 10 minutes or until chicken-vegetable mixture is bubbling and biscuits are slightly browned on top. To serve, place ramekins on individual plates, as they will be too hot to handle.