Preheat oven to 400.
Grease a small casserole dish.
Dice chicken into 1/2" cubes.
In a large skillet, melt butter over medium heat.
Cook diced onions until transparent.
Add chicken, water, potatoes, soup, poultry seasoning and peas and carrots.
Stir and cook over medium heat until ingredients are warm (10-15 minutes). If mixture looks too thick, slowly add a little more water until desired consistency is reached.
Cut biscuits into quarters.
Transfer chicken mixture to prepared dish.
Place biscuit pieces over chicken mixture.
Brush tops of biscuits with melted butter.
Bake for 10 minutes.
Cover with aluminum foil and bake for 15 more minutes until golden brown.