Rinse the corned beef brisket and place it in a large stockpot. Cover with beef stock and add the onion, garlic and spices to the pot. (If your corned beef comes with a seasoning packet, you do have the option of using that instead of the spices listed here.) Place the dried split peas into a pudding bag
, or wrap them in the cheesecloth, tying the cheesecloth loosely so that the peas have room to expand. Push the bag down into the liquid, adding a cup or two of water to make sure everything is submerged. Cover the pot with a lid and bring everything to a simmer. Lower the heat and simmer for 1 hour and 30 minutes.