Layer the chopped onion on the bottom of your crockpot.
Place the chicken thighs on top of the chopped onion in a single layer.
In a mixing bowl, place 1 can of cream of chicken soup.
Pour a can of cream of celery soup into the mixing bowl.
Add 1 tsp of poultry seasoning to the mixing bowl.
Sprinkle in 2 tablespoons of chopped fresh parsley.
Add black pepper to taste.
Stir all of the ingredients in the mixing bowl, and pour over top of the chicken thighs in the crockpot.
Pour 2 cups of chicken broth over top of the chicken.
Set the crockpot to high for 5 hours and close the lid.
Do not open the lid until you have just 1 hour of cook time left on the crockpot’s display. With 1 hour left, open the lid and pour in 2 cups of mixed vegetables that have been defrosted. Mix them into the crockpot well, shredding the chicken thighs as you stir.
Open a can of refrigerated biscuits, and flatten each one. Cut each biscuits into 4 long slices.
Layer the biscuits on the top of the chicken mixture in the crockpot.
Let the biscuits cook for the remaining hour of cook time, and then stir the mixture together well to incorporate the dumplings into the chicken mixture.