You'll also find this recipe on page 143 of the FFS! Cookbook.
Working out macros for this is pretty much impossible. We treat the fat (tallow) as a direct replacement for other cooking oils like lard, so we use those macros. The bone broth itself is mostly protein and will be very close to 0g carbs.
750g Meaty Bones (we get these from Morrisons)
2 Marrow Bones
2 Medium Carrots
1 small bunch of Flat Leaf Parsley or any other fresh herb of choice
1.5-2 litres Boiling Water
1 tsp Pink Himalayan / Rock / Sea Salt
Pan fry the bones and carrots in a large frying pan over a medium / high heat. We used the Sear function on the Ninja Foodi.
Once the bones have browned on each side, transfer all of the ingredients to a slow cooker and cover the bones with boiling water.
Add the salt and parsley and allow to cook for a minimum of 24 hours.
Remove the meat and carrots but leave the bones in to cook for a further 12 hours. Refrigerate the meat in a container to allow any fat to solidify. Once cooled, you'll be able to remove the fat from the meat easily.
Remove the layer of fat from the stock and place with any fat from the meat into a pan and heat over a medium heat. Allow any water to cook away - it'll stop spitting once all the liquid has been cooked away.
Allow the fat to cool and strain through a stainless steel sieve to remove any food and store in the fridge. This fat can be used when roasting vegetables or frying.
Reheat the stock and allow to reduce over a gentle heat for 15-20 minutes.
The stock can be stored in the fridge. When you want a cup of bone broth, take about 100ml out and reheat.