Place the chicken breasts, chicken broth, carrots, celery, onion, thyme, garlic powder, salt, and pepper in the slow cooker. Stir to combine the ingredients evenly.
Cover and cook on low for 6 hours until the chicken is tender and shreds easily.
Remove the chicken from the slow cooker, shred it with two forks, and return it to the pot. Add the egg noodles and stir.
Cover and cook on high for 30 minutes until the noodles are soft.
While the noodles finish cooking, preheat the oven to 425 degrees. In a mixing bowl, combine the flour, baking powder, and salt. Cut in the cold butter until the mixture looks like coarse crumbs.
Stir in the milk until a soft dough forms. Drop spoonfuls of dough onto a baking sheet and bake for 12 to 15 minutes until golden.
Brush the hot biscuits with melted butter and serve them alongside the soup.