Place potatoes, 3/4 cup of the stock, the garlic, rosemary, thyme, and half of the salt. Book on low 6-7 hours or high 3-4 hours. I recommend cooking it on low. On the high setting, you might start browning the potatoes slightly.
Every hour, if you can stir the potatoes.
Once the potatoes are tender, add the remaining ingredients except for the leftover stock and parsley. Mash until they are the consistency you like. If you like them a little looser, add the remaining stock. Taste and adjust seasoning if necessary. Garnish with parsley (optional).