Using a standard slow cooker, add 1½ cups broth, diced onion, carrots, celery, garlic, thyme, salt and pepper; stir until well combined. Add chicken thighs. Cover and cook on low for 5 hours.

Remove chicken from slow cooker and transfer to a large plate or cutting board. Using 2 forks, shred chicken. Return shredded chicken to slow cooker.

Using a small bowl, add remaining ½ cup broth, heavy cream and flour; whisk until smooth. Add this mixture to slow cooker along with peas and chopped parsley; stir until well combined.

Using a medium mixing bowl, combine the flour, baking powder, salt, pepper and thyme; stir until well combined.

Cut the butter into ½" cubes and add to the bowl of dry ingredients.

Using a pastry cutter (or two table knives), cut the butter into the dry ingredients until butter pieces are size of peas.

Add the buttermilk and stir until absorbed. (Note: This dough is fairly sticky.)

Using two spoons, drop the dough in tablespoons on top of chicken mixture. Cover slow cooker and continue cooking on low for 1½-2 more hours, or until a toothpick inserted into the dumplings comes out clean.