If you want this dessert to have a consistency more like porridge serve it hot or don't let it thicken that much when cooking.

Otherwise, let it cool down and put it in the fridge the consistency becomes more similar to pudding.

Pro tip:
In case you like to add some fruits, I'd recommend adding them when the pudding is done already.
Red berry compote goes great with it and you can easily prepare it by heating up frozen berries in a pot, adding some water & gelatin and boiling it until it thickens.  Then, let it cool down. Holds in the fridge for 1-2 weeks.

You may also try out one of the other optional ingredients, a combination of them or leaving out the cinnamon. I only sprinkled some cacao powder on top here and mixed it in with the spoon afterwards.

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.

You can check if the pork back is done to your preference by using a meat thermometer.
If the core temperature reaches 70-75°C (158-167°F) the meat is medium-well. If its core temperature reaches 80-85°C (176-185°F) it is well done, but not as tender anymore.

In addition, you may also use the juice from the baking tray to make a delicious gravy sauce or simply pour it over the vegetables you may have made as a side dish.
For a sauce, simply fry 2 onions with butter in a pan (until golden brown), then pour in the meat juice and let everything cook until it is reduced to your desired thickness.
If you don't want to use onions, replace them with 100ml (about 3oz) cream in order to get thickness to the sauce.

The method in this recipe works with nearly any type of meat, but best with cuts that contain fat & some gristle like beef shank or ham hock.

You may also enhance the sauce by deglazing the onions with red wine and let it cook for a minute before adding the meat stock.

Pro Tip: For some awesome vegetables on the side, cook them in a pot or the microwave until they are nearly done. Put the finished meat on a plate and cover it with aluminium foil to keep it warm. Then, shortly fry the vegetables on medium-high heat in the remaining butter and pork grease in the pan.

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.

You could also use bacon bits and fry the eggs in the grease instead of the butter, or even wrap the eggs in bacon.