This is my recipe for this British classic and I like it a lot. I was initially inspired by a version I read about in Chef April Bloomfield's book A Girl and Her Pig. This is not her recipe, though. It's an amalgam of several I've read in various books, as well as from my own, albeit limited, experience eating these meatballs. If you are in a hurry, you can indeed start with ground pork or venison -- something meat processors really love to give you a lot of if you don't butcher your own deer. You must make sure that the ground meat has some fat in it, otherwise your meatballs will be dry and sad.
Take the caul fat out if you are using it and soak it in tepid water with a little salt tossed in, maybe a teaspoon. This will help it loosen.
Cut the venison, bacon and liver into 1-inch chunks and freeze for 30 minutes to an hour, until they are about half-frozen. Grind the oats in a food processor or spice grinder into a coarse meal like coarse corn meal. Or, just use breadcrumbs.
When the meat is ready, mix it with the onions and grind on a medium die, 6 mm if you have one, or the "coarse" on a Kitchenaid grinder. Put the meat in a bowl and mix with the oats and all the herbs and spices. Preheat the oven to 375°F.
Gently unravel the caul fat into one layer and lay it on a clean work surface. Form balls with the meat mixture of about racquetball size, a little smaller than a baseball or the size of a small orange. You want them big. Place the ball on the caul fat and slice enough of the caul around it to wrap the ball completely. Arrange seam side down in a baking dish. If you can't find caul fat and are using thin bacon, wrap the balls in bacon strips until you have them covered. Repeat until you have all the meat done.
Bake uncovered in an oven for 40 to 50 minutes, basting every 10 to 15 minutes with the stock. Serve with mashed potatoes and peas.
The caul fat matters here. Your meatballs will be far better with it than with the thin bacon, but they'll still work with the bacon. Most butchers will have caul frozen, and even some larger supermarkets should be able to order it for you. Caul fat can be frozen and thawed several times with few ill effects, so you can keep some on hand for whenever you want to make this or its French cousin, crepinettes.