1. Lightly grease the slow cooker. Place chicken breasts or thighs in the bottom, then add chopped onion, celery, and minced garlic.

2. In a bowl, whisk together condensed cream of chicken soup, chicken broth, milk, dried thyme, dried rosemary, salt, and black pepper until smooth.

3. Pour the creamy mixture over the chicken and aromatics in the slow cooker.

4. Cover and cook on LOW for 6-8 hours or on HIGH for 3-4 hours, until the chicken is cooked through and very tender.

5. About 30 minutes before serving, stir in the mixed frozen vegetables and let them heat through.

6. Shred the cooked chicken directly in the slow cooker and stir to combine with the sauce and vegetables.

7. If the sauce needs thickening, make a slurry by mixing 1 tablespoon cornstarch with a little cold water, stir it into the hot filling, and cook on HIGH for 15-20 minutes until thickened.

8. For biscuit topping in the slow cooker, place biscuit dough on top during the last 30-45 minutes if your lid allows space, and cook until biscuits are golden and set.

9. For puff pastry or pie crust topping, transfer hot filling to an oven-safe dish, cover with thawed puff pastry or pie crust, cut slits for steam, and bake at 375°F/190°C for 20-30 minutes until golden.

10. For mashed potato topping, spread hot mashed potatoes over the filling and serve.