Go to your butcher or grocery store and buy beef marrow bones and beef feet.

You can roast the beef marrow bones for more flavour, but this is optional.

Fill your slow cooker with the bones.

Chop up 1 stick of celery, 1 whole onion, and 1 head of garlic. Place in the slow cooker.

Add 1 tbsp of raw apple cider vinegar to the slow cooker. This is optional, but it is said to help extract more minerals.

Fill the slow cooker with water and season with salt and pepper.

Turn your slow cooker to low and cook for at least 48 hours. After 48 hours, put some spoonfuls of the broth into a bowl and place in the fridge. If the broth gels, it is ready. If it doesn't gel, continue to cook.

When the broth is done cooking, pour it through a colander.

Freeze the broth in ice cube trays, then put the cubes in a bag. When you are ready to use the broth, place a couple of ice cubes in a pot, turn the heat to low, and slowly heat up the broth. Add parsley to taste.