Preheat an oven to 350, then roast the potatoes until just tender. Cool the potatoes, then peel and dice ¼ inch, you should end up with about 2 cups.
In a bowl, toss the potatoes with the diced venison heart thoroughly, you don't want to make mashed potatoes, but don't be afraid to smush it a bit to cover everything with a decent layer of starch, which helps make the crusty part everyone loves about hash.
Heat the oil or lard in a cast iron skillet or other non-stick pan until lightly smoking. Add the potato-heart mixture, season lightly with salt and pepper, then press the mixture down and cook on medium-low heat until a golden brown crust forms on the bottom and the mixture moves as one, about 5 minutes.
Carefully flip the mixture if you're adept at flipping things in pans, or alternately use the safe and less exciting way of inverting the hash onto a plate, then sliding back into the pan to cook the other side and form a crust. When a nice crust has formed on the other side, the hash is ready, carefully transfer to a plate(s) and serve immediately.