Slow-Cooker Korean Beef Tacos

In the bowl of a slow cooker, add the skirt steak, 1 red onion cut in half, soy sauce, white wine, brown sugar, black pepper and 3 garlic cloves that have been smashed. Mix ingredients together to coat the meat. Cook on low for 9 hours. Meanwhile, cut the tomatillos in half and place on a sheet pan lined with parchment paper. Broil for 10 minutes, flipping about half way through to brown both sides and prevent burning. Set aside to cool for a few minutes. In the bowl of a food processor add tomatillos, 1 smashed garlic clove, 1 cup chopped cilantro, half of a red onion roughly chopped, juice of 2 limes, scallions and salt. Pulse until well combined but not pulverized. Keep in refrigerator. After 9 hours, transfer the beef to a cutting board and remove any excess fat. Shred the beef using 2 forks and mix in a bowl with 1 to 2 tbsp of the braising liquid. Warm tortillas in a dry skillet. Serve with tomatillo salsa verde and garnish with chopped cilantro, diced red onion and cucumbers.