Here's how I did a batch last week.......
1) Season liberally with salt, black pepper, and garlic appx. one day ahead of time. I used the rear shanks of a small doe & checked to make sure they'd fit in the Dutch oven. They did.....barely
2) Preheat the Dutch oven (or roasting pan if your shanks are too big) on medium heat at the most. Add your oil....I used duck fat and some pork lard for mine. But bacon grease, butter, or olive oil will work if you don't have some animal fat of some type. Pat dry (important!!) and brown the meat on all sides that'll fit in the pan. I set the meat down for about 5 minutes a side to get a good browning, and rotated around.
3) Remove meat, add 1/2 of a sliced white or yellow onion & scrape the pan very well. A pinch of salt will release the moisture from the onions. Point of this is to deglaze some of the browned bits off the bottom. Once the onions caramelize a bit, add about 4 cloves of garlic thinly sliced. Pepper the crap out of it, add another pinch of salt, then stir in about a can of tomato paste.
4) Once the tomato paste combines with the onions and garlic into a sticky glob, turn the heat to high and add a quart of stock. It'll hiss and sizzle and bubble.....scrape the bottom of the pan clean and break up all the remaining browned bits and incorporate the tomato sauce glob. This is a good point to add about a cup or two of good red wine (I like a merlot or cabernet for this). Cook and simmer on medium heat for about 10 minutes, add a bay leaf or 3, and shove the shanks in. The liquid should come up to at least halfway up the meat, without covering it entirely.
5) Put a lid on the pot and stick it in a 225° oven for at least 6 hours.
I did mine overnight, and turned the oven off when I left for work. It cooled down during the day so that when we got home, we could pull the meat apart from the bones, shred it up a bit, and reheated the sauce & meat all together. It serves very nicely over whatever carbs you want.....smashed potatoes, or rice, or bowtie pasta, or a parmesan polenta.
It's delicious and will make you second guess ever throwing shanks in a grind pile again.