Make a dry rub: In a ziplock bag or small bowl combine the sugar, salt, cayenne pepper, granulated garlic, fresh ground black pepper and thyme and mix well.
Next add 1/3 of the dry rub, about 3 tablespoons of the cassareep and the chopped garlic to the beef. Mix well then let marinate for at least 30 minutes before cooking.
Add another 1/3 of the dry rub to the oxtail, followed by about 3 tablespoons of cassareep and let that marinate for at least 30 minutes before cooking. Do the same for the cow heel.
Peel and dice the onions and set aside.
When ready to cook, heat a large stock pot on high heat. When the pot is hot add about 2 tablespoons of oil. Then add all of the onions (if using). Cook for onions for about 2-3 minutes or until translucent.
Add the seasoned beef, cinnamon, cloves (if not putting the cloves in a pouch) and continue to sauté until all pieces of the beef are brown all over. You may brown the beef in batches if necessary.
Once the beef is brown, add about 6 cups of water to the beef and bring to a boil, then reduce heat to low and let simmer.
While the beef if simmering, bring about 1 tbsp oil up to temperature in a pressure cooker on high heat then add about a tablespoon of oil and the seasoned cow heel.
Cook the cowheel for a few minutes turning often, then add 5 cups of water to the pressure cooker. Cover and pressure cook until the cow heel is tender but not completely falling off the bone, this should take about 45 minutes depending on the size of the cow heel but I recommend checking the tenderness of the meat after 30 minutes of pressure cooking. You are looking for fork tender but not fall off the bone tender.
Follow the same steps to pressure cook the oxtail as you did with the cow heel. If you have a large enough pressure cooker you may cook the oxtail and cow heel together but start by pressure cooking the cow heel first for 45 minutes, then adding the oxtail and continuing for another 45 minutes.
Once the oxtail and cow heel are tender add them to the pot with the beef. Mix to combine. You may add 2-3 cups of water here if need, but just enough to cover the meat in the pot.
Then add the remaining 1/2 cup of cassareep, the wiri wiri peppers and your pouch of cloves (if you are doing that). Increase the heat to high and bring pot back up to a roaring boiling. Let it boil for 10 to 15 minutes. Then, reduce heat to low and simmer until all the meat is falling off the bone tender, about 2.5 hrs.
About half way through taste the pepperpot and check for color. At this point you may add a pinch of salt, about 1/4 cup more cassareep if it is not dark enough and 1/4 cup more sugar if need (but thread lightly you don't want it to be overly sweet). You may also pop open your wiri wiri peppers for additional heat.
Pepperpot is traditionally served with cassava bread or Guyanese Plait Bread.