To begin, I placed chicken in 4 cups of water and set on med.-high heat. Throw in onion, celery, potato, and carrots. When chicken is done, remove from pot to cool. Skim and discard any fat from top of water.
While chicken is cooling, make a roux. To do this heat butter and flour in a skillet to make a blonde roux. Stir often so that roux doesn't go dark.
Once chicken is cooled, remove skin and bones. Dice breast meat and add back to the pot. Add seasonings and roux, and reduce heat to a low simmer. Turn oven on to temperature recommended to cook biscuits.
When vegetables are tender and sauce has thickened add peas and transfer to a casserole dish; top with biscuits. I placed them one right next to the other so that they would squish together as they baked. Remove from oven once biscuits turn golden in color.
If your stew is not as thick as you like, you may add a tablespoon of cornstarch which works as a thickening agent, but don't just throw cornstarch into the pot or you'll get lumps. Mix it in a bowl with a tablespoon or two of water, first, so that you smooth out any lumps. Bring your stew back up to a simmer if you add cornstarch and let it cook for about 5 minutes. Also keep in mind that the stew will thicken as it cools so it's kind of difficult to gauge how thick your sauce will be right off. You want it to coat the back of a spoon, if it runs off you've got a soup not a stew.