How to make it
Mix oyster sauce with cornstarch, add chicken pieces and stir to coat. Set aside.
Preheat the oven to 375°F. Heat oil in a large ovenproof casserole, add onion and pancetta/bacon and cook over medium-low heat 5 minutes until softened. Increase heat, add chicken pieces, and cook, turning for 2–3 minutes. Add garlic and cook 1 additional minute.
Add remaining vegetables to casserole along with stock. Bring to simmer, stirring well. Cover and place in oven 30 minutes.
Cut potatoes into 1/4-inch slices. Increase oven temperature 400°F. Take hot casserole from oven, remove lid, and arrange potato slices over top. Brush with melted butter then cook for another 30-40 minutes, until potatoes are golden brown. Sprinkle with parsley before serving.