Anglo-Indian Beef (Or Lamb) Stir-Fry - cooking recipe

Ingredients

1 1 lb leftover beef roast or 1 lb leftover lamb roast
1 tablespoon rice vinegar or 1 tablespoon apple cider vinegar
1 1/4 teaspoons salt, divided
3/4 teaspoon ground turmeric, divided
2 medium russet potatoes
6 tablespoons canola oil, divided
1 medium yellow onion, halved and thinly sliced, about 1 1/2 cups
1 1/2 tablespoons minced fresh ginger
1/4 teaspoon cayenne

Preparation

If using raw beef, freeze 20 minutes and slice paper-thin. (I would buy beef sliced for bulgogi). Rub the beef with the vinegar, 1 tsp salt and 1/2 tsp turmeric. (With leftover roast, I omitted the salt, but used the turmeric and vinegar. I also sliced it somewhat thicker).
Bring the whole potatoes to a boil in slightly salted water to cover. Boil for 5 minutes, then remove from heat and let sit in the hot water for 15 minutes. The potatoes will be perfectly done. (Or cook potatoes by your preferred method).
Peel the potatoes and cut into 6 to 8 wedges each. Coat with the remaining 1/4 tsp turmeric and 1/4 tsp salt.
Heat 3 tbl oil in a large wok and fry the onion and ginger until slightly softened.
Add the cayenne and the marinated beef (I also added the marinade). Cook over high heat for 5 to 8 minutes or until tender. If not sufficiently tender, add 1/2 cup water and cook over medium-low heat until it's done to your likeness. (With the leftover roast, you really just want to get it warmed through, so watch your cooking time).
Meanwhile, heat the remaining 3 tbl oil in a large skillet and gently fry the potato wedges over low heat (I used medium heat) until golden brown and crisp.
Serve meat with the potato wedges. To be authentically Anglo-Indian, serve some ketchup on the side.