Of course, you may also use any other cheese you prefer, like mozzarella, parmesan or cheddar.

The pulled pork turns out great if you use pork neck instead of shoulder, too. It may be even better as pork neck usually is a little fattier then shoulder and therefore juicier & more flavorful.

The additional egg in the ground beef mixture helps to hold everything together. I didn't do this here, but highly recommend it as the result will be better that way.

Also, deep frying is the best method to cook these, because they get fried more evenly and are done faster.

Serve with any side dish you like - e.g. oven baked broccoli, fried string beans or cauliflower mash. I simply added some low carb ketchup & mayo.

Tip: If you want to go full pro add a layer of "breading" around the ground beef. You could use crunched pork rinds / crispy bacon bits for that.

You probably could skip the meat hammer step if your beef liver pieces already are pretty flat (about 0.5cm / 0.2in of thickness).

If they are way too thick, lay them on the cutting board.
Then, cut from one side with a sharp knife until you nearly reached the end of the other side.
Now, you can simply fold out the pieces and have thinner ones.

At step 3 I used frozen spinach which I thawed & pre-cooked in the microwave for about 3 minutes while beating up the liver:

Of course, you may also use different stuffings.

One idea that I've had was pizza stuffing with tomato paste or fresh tomatoes, mozzarella cheese & Italian / Mediterranean herbs (oregano, rosemary, thyme). Maybe with some additional ground beef, pepperoni, fried chicken or even pulled pork.

If you want to render the kidney fat cut it into small bits or mince it in a food processor.
Then, put it into a pot or big pan on low heat and wait for all the fat to get out while stirring occasionally.

You can see that it's done when there is clear fat on the bottom with crispy bits on top.

Now, you can remove these floating bits by pouring all content through a cheesecloth or fabric into another pot.
When the fat is cooled, pour it into mason jars and keep them in the fridge.

For a dairy free alternative, just replace the butter with coconut oil or lard.

I also added some mayonnaise and an avocado that I sprinkled with some salt & pepper on the side.

If you want a great sauce to go with your meatballs simply add about 150 gram cream to the pan with the remaining grease after frying and taking the meatballs out.
Then, let the cream cook on medium heat while stirring until it is reduced to your desired thickness. This works great with coconut milk/cream, too.
In case you don't want to use cream, slice 2-3 onions and cook them on low-medium heat in the remaining grease until they start to dissolve and everything thickens to a sauce.

I used frozen brussel sprouts and thawed them in the microwave for 10 minutes, while the liver and eggs were cooking.
You could also use fresh ones and cook them in advance to preparing the liver.