Cut the potatoes in half in the width, then cut into long, thin slices — about two to three times as thick as you would cut potato chips.

Heat oil to 350 degrees Fahrenheit (175 degrees Celsius) in a large pot. Fry the potatoes in batches until crispy and golden, about seven to 10 minutes. Remove to a paper-towel-lined dish to drain, and immediately add salt and pepper.

For the mushroom sauce: Using a sharp knife, cut the meat off the lamb shanks, removing as much silver skin as you can, then dice the meat. Heat a skillet with oil and brown the meat. Season with salt and pepper, and continue to brown on all sides, about five minutes. Remove the meat from the pan and set aside.

Add the mushrooms to the pan along with another pinch of salt. Sauté until browned. Add lamb and accumulated juices back in. Add in chicken stock, using a spoon or spatula to scrape any brown bits from the bottom of the pan. Simmer for five minutes, then taste and adjust seasoning.

Add potato starch slurry to the pan and cook two to three minutes more, until the sauce has reached a gravy-like consistency.

Spoon mushroom sauce over potatoes immediately before serving.