Begin by running the oxtails under cool water. This will help remove some of the blood and debris. Then, dry them with a paper towel.
Peel your onions and other vegetables, cutting them into small chunks. Cut the leeks lengthwise and slice your bacon slices in half.
Fry your bacon, then remove with a slotted spoon and set aside, leaving the bacon fat in the pan.
Add your oxtails to the pan and brown them.
Add your vegetable to the saucepan, stirring carefully. Let them cook for about five minutes, then add your spices.
In a large stockpot, combine all ingredients, then bring the mixture to a boil.
Let it cook at a simmer for about two hours. Stir regularly and replace evaporated water as needed.
Serve with parsley as a garnish.