All ingredients are readily available at Tesco, Sainsbury’s, Waitrose, ASDA, and Morrisons. Bone-in, skinless chicken thighs are in the fresh meat section, Kalamata olives in the deli or international aisle, and canned diced tomatoes in the pantry section. Fresh onions, garlic, and dried oregano can be found in the produce and spice sections. Olive oil is available in the pantry aisle.