1. To marinate the meat, place the turkey legs in a large bowl or baking dish. Add all the ingredients in the “to marinate” section. Massage the marinade into the meat with your hands. Cover and place in the fridge for an hour to overnight.
2. Set oven to 425°F. Place the turkey on a baking sheet. Roast for about 15 minutes until the skin begins to brown. Remove from oven, and turn heat down to 300°F.
3. In a large dutch oven over medium heat, add a few tablespoons of olive oil. Add the onion and let cook for a minute until translucent. Add the garlic, season with salt and pepper and let cook for a minute until soft and fragrant. Add the vinegar, chicken broth, beer and turkey. Cover and transfer to the 300°F oven. Let cook for 4-5 hours until tender and falling apart.
4. Meanwhile, make the sauce. Place all sauce ingredients over medium-high heat. Whisk continuously until sauce is reduced by about one third and thickens, about 10-15 minutes.