Set pressure cooker to "sear", add oil, and press "start/stop".
When hot, add butter and melt. Add chicken and cook until golden brown. Remove chicken, set aside.
Add lemon juice, capers, and stock. Return chicken to cooker.
Close and lock lid, set pressure cooker to "poultry", and adjust time to 5 minutes. Press "start/stop".
When done, quick release and make sure all pressure is released before opening lid. Carefully open lid, check seasoning, and add salt and pepper, if needed. Serve hot with mash potatoes or rice.
Garnish with parsley.