Marinate with your marinade of choice, or try this: To 1 quart of buttermilk add 3.75 Tbls Morton kosher salt. Take 1 cup of this and put it in your blender with 2-3 cloves of garlic, 3-4 bay leaves, 1 Tbls coriander, and purée well. Mix this with the remaining 3 cups buttermilk and marinate the roast in it overnight.
When ready to cook, remove the roast from the marinade and pat it dry. Get your smoker going and low/slow the roast to an internal of ~120-125. Meanwhile, slice 3-4 peeled onions and scrape and slice 1 carrot; peel and smash 3 cloves of garlic.
If you don't have a dutch oven suitable for the cooker use a wide piece of HD foil. (Put the foil on an unlipped sheetpan or flip a lipped sheetpan over and use its bottom.) Place half the onions, carrot and garlic on the foil. Sprinkle lightly with salt and add a good dose of pepper. Top the pile with a few sprigs of fresh thyme (or use about 1.5 Tbls of dry) and a couple small fresh rosemary sprigs.
Have ready 1 can of diced tomatoes in juice, a cup or do of cheap white wine, and about 2-3 cups low-salt chicken stock. When the roast hits your target bring it inside and place on top of the vegs on the foil. Bring the sides of the foil up, and top the roast with the rest of the onions, carot and smashed garlic. Add a thyme sprig or two and another rosemary sprig. Dump the tomatoes on and around the roast and add the wine. Add enough stock so that it comes better than halfway up the sides of the roast. Sprinkle with pepper and about a tsp of sugar. Add 3/4 of a stick of good unsalted butter, cut into pieces, scattered. Top with a piece of foil and crimp the foil pieces together tightly, leaving room around and above the roast. Cart your pan out to the smoker and carefully slide the package onto the top grate. Raise your temp to 275-295 or so. Cook 1.5-2 hours then carefully unseal to check the tenderness and get a feel for things. It will likely need 1.5-2 hours more but this is hard to say.
[If you have a covered dutch oven use it -- makes it much easier.]
When the roast is very tender and falling apart you can remove it from the pot and let it cool, separately coolong the pot contents. If you wish, chill both when cool and finish the next day. (Remove some but not all of the fat that will have congealed on top while the sauce is in the fridge.)
Skim some fat from the sauce (if you are eating the same day) and remove the thyme and rosemary sprigs, then purée it well. Place in a pot and bring to a short simmer. Adjust seasoning. Add the meat to the pot, either as is, or broken up, chopped or pulled a bit. Barely simmer to blend flavors, about 5 min; serve.
