In a small mixing bowl mix ½ teaspoon baking soda with a tablespoon of water to form a slurry. In large bowl, toss beef with baking soda mixture and ½ teaspoon salt until thoroughly combined. Set aside.
Heat the oil in a hot frying pan and add the beef. Stir over high heat until golden-brown. Using a colander, drain any fat or liquid from the meat and return it to the pan. Sprinkle the flour over the meat and coat well. Remove from the pan and set aside.
Add the onions, celery, and carrots to the pan and fry until beginning to soften. Return the beef to the pan.
Add the stock & soy sauce to the pan, mix well to avoid any lumps. Bring to the boil, stirring constantly until thickened, then add the mushrooms and parsley. Tasate for seasoning and season with salt and peppe as needed. Cover with a lid and simmer for 30 minutes, or until the mince is tender.
While the filling cooks, start the potatoes - Boil the potato slices in salted water for about 4-5 minutes or until they start to soften. Drain them carefully into a colander and leave to cool.
Preheat the oven to 425f/220C.
Pour the beef mixture into a shallow casserole dish. Arrange a layer of the blanched potato on top of the beef mixture.
Thoroughly mix the flour into the cream (being sure not to leave any lumps). In a saucepan, heat up the cream garlic, nutmeg, and some salt and pepper. bring to a simmer and allow to thicken.
Pour half of the cream mixture over the first layer of potatoes already in the pan. Arrange the remaining potatoes on top, seasoning between the layers. Pour over the remaining cream and sprinkle over the cheese.
Bake in the preheated oven for about 30 minutes, or until golden-brown.
Don’t skip the baking soda step. This will ensure your beef stays nice and moist.
When browning the beef, only cook until the pink is gone. You don’t want to overcook it.
For extra depth of flavor, allow the vegetables to brown once softened and then scrape the pan to remove any crispy bits when adding the stock.
Allow the sauce to thicken well before assembling. You don’t want a soupy mess.