Let the short ribs sit at room temperature. Preheat the oven to 350°F. Season on both sides. Dredge all sides with flour. Heat a dutch oven over high heat.
Add oil. Braise the short ribs on each side until browned. Remove to a plate and reduce the heat to medium.
Sauté the veggies for 4 to 5 minutes. Add garlic and cook 1 minute. Pour Guinness over the vegetables. Stir in beef stock, cover and bake until tender.
Transfer the short ribs to a platter. Blend the vegetables and liquid into a smooth sauce. Pour the sauce over the short ribs and serve.