Preheat your oven to 190°C.
Place the peeled and chopped potatoes into a large pot of salted water. Bring to a boil and cook for 15 minutes, or until the potatoes are completely fork-tender. Drain well and return them to the warm pot.
While the potatoes are boiling, heat the oil in a large, deep oven-safe skillet (or a regular pot) over medium-high heat.
Add the chopped onion and minced garlic, sautéing for 3 to 4 minutes until soft and fragrant.
Add the ostrich mince and diced carrots to the skillet. Use a wooden spoon to break up the mince as it cooks. Sauté for about 6 to 8 minutes until the mince is completely browned.
Stir in the tomato paste and your seasoning (thyme or braai salt), cooking for 1 minute to release the flavours.
Pour in the Ina Paarman chicken stock and add the drained brown lentils. Lower the heat to medium-low and let the mixture simmer gently for 8 to 10 minutes until the liquid reduces into a thick, glossy gravy.
Stir in the frozen peas and corn during the last 2 minutes of simmering. Turn off the heat.
Take your warm, drained potatoes and mash them roughly with the butter, salt, and white pepper.
Stir in the full tub of cottage cheese and mash until thoroughly combined.
Let the mash cool for 2 minutes (so you don't cook the eggs prematurely), then gently fold and whisk in the two whisked egg whites and milk until the topping is smooth, light, and fluffy.
If your skillet isn't oven-safe, transfer the ostrich filling into a medium-sized baking dish (approx. 20 x 30cm).
Spoon the high-protein mash evenly over the top of the mince. Use the back of a fork to create ridges across the surface - these ridges will catch the heat and turn crispy.
Bake in the preheated oven for 30 to 35 minutes until the gravy bubbles up around the edges and the potato topping turns beautifully golden brown. Let it cool for 5 minutes before slicing.