Heat oil over Medium heat (5). Add the Onion and Garlic. Cook for about 3 minutes. Then remove from the pan and set aside with the Carrots, Parsnips, Salt, Pepper and Thyme
Turn heat up to Medium High (7) and add the Chicken pieces (start with skin side down) in a single layer and cook each side for 5-7 minutes until they are lightly browned
Turn the heat up to High (9) and add the Onions, Carrots, Parsnips, Thyme, Salt and Pepper. Pour in the Irish stout and bring to a boil. Reduce the heat to Medium Low (3), cover and allow to simmer for 35 minutes
Add the Mushrooms and Peas and leave covered for another 10 minutes
Remove the cover (to allow the juices to slightly thicken) and keep cooking for an additional 10 minutes. You’ll want the internal temp of the thickest part of the chicken to be at least 165 degrees F.