Preheat your oven to 375°F (190°C). In a large mixing bowl, combine the shredded chicken, frozen mixed vegetables, chicken broth, heavy cream, garlic powder, onion powder, thyme, black pepper, and salt. Mix well until all ingredients are evenly coated.
Pour the chicken mixture into a greased 9x13-inch baking dish. Spread it out evenly, making sure it’s uniform.
In a separate bowl, whisk together the flour, baking powder, baking soda, and salt. Cut in the cold, cubed butter until the mixture resembles coarse crumbs. Gradually add the buttermilk and stir until just combined. The dough will be slightly sticky.
Using a spoon or a cookie scoop, drop spoonfuls of dumpling dough over the chicken mixture. Make sure to leave some space between each dumpling as they will rise while baking.
Sprinkle the shredded cheddar cheese evenly over the dumplings.
Cover the baking dish loosely with aluminum foil and bake for 25 minutes. Then, remove the foil and continue to bake for an additional 15-20 minutes, or until the dumplings are puffed and golden brown, and the cheese is bubbly.
Once baked, let the casserole cool for a few minutes. Sprinkle with chopped fresh parsley before serving for added color and flavor.