• Preheat the oven to 300°F
• Season the short ribs with salt and pepper. Heat a Dutch oven or other large deep pan over medium high heat. Add the oil and heat for a couple minutes. Working in batches, brown the short ribs on all sides, 5 or 6 minutes per batch. Transfer the ribs to a plate after browning each batch. Add additional oil if needed.
• When all the ribs have been browned, pour off all but 2 tablespoons of the remaining fat from the pan. Add the carrots, onion, celery, garlic, herb bundle, bay leaf and peppercorns. Stir and scrape up any of the flavorful bits from the bottom of the pan.
• Add the beer and bring to a boil, cook for 5 minutes to reduce the liquid and cook off the alcohol from the beer. Return the beef short ribs to the pan with the accumulated juices, arranging the beef in one layer, then add the beef broth. 
• Cover the pot with its lid and transfer to the preheated oven and braise for 3 hours. Transfer the pot from the oven to the counter top, adjust the lid slightly off-pan to allow the steam to escape and let the beef ribs cool for 1 hour. 

Set the oven to the ‘warm-and-hold’ setting or it’s lowest temperature.

• Using a slotted spatula or large spoon carefully remove the beef ribs from the pot to a platter and cover loosely with foil and set the platter in the warm oven while preparing the sauce.
• Pour the cooking liquids through a fine-mesh strainer into a medium-size saucepan. Place the saucepan over medium-high heat and boil until reduced to 2 cups, about 15 minutes.
• While the liquids are reducing, mix the butter and flour together in a small dish, mashing with the back of a tablespoon to make a smooth paste. 
• When the liquid has fully reduced to 2 cups, stir in the Dijon mustard and the Worcestershire sauce. Remove from the heat and whisk the butter/flour paste into the liquid until melted into the sauce. Return the pan to a medium heat, continue cooking and whisking for another 2 minutes to a smooth sauce. Transfer the sauce to a dish or gravy pitcher
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