This traditional beef carbonnade (Flemish stew) is made with beef chuck roast and seasoned with caramelized onions, beef broth and dark ale, which lends sweet and sour flavors to the Belgian beef stew.
Trim excess fat from the beef chuck roast and slice the meat across the grain into ½" x 2" long. Season the beef with the kosher salt and pepper. Set aside.
Heat a Dutch oven over medium high heat. Add 1 tablespoon of butter and the olive oil. When the butter has melted, add the beef in 2-3 batches and brown, searing the strips of meat on all sides. Transfer to a rimmed baking sheet and continue to brown the meat.
Add the bacon to the pot and cook, stirring occasionally until it's crisp. Transfer bacon to a dish lined with a paper towel to soak up excess grease.
Discard all but 2 tablespoons of grease from the dutch oven and add the sliced onions. Cook, stirring occasionally with the lid slightly askew on the pot so steam can escape. Cook the onions for 25-30 minutes or until they're caramelized and golden.
Deglaze the pot with 1 cup of the lager and cook for 4-5 minutes, scraping up the browned bits (fond) from the bottom of the pot.
Add the brown sugar, malt vinegar, garlic, thyme, bay leaves and carrots. Stir to combine and add the remainder of the beef broth and lager.
Add the reserved beef and any drippings and stir to combine. Bring the carbonnade to a boil, then cover tightly with a lid and put in the oven to braise for about 1½ hours.
With the back of a fork, mash together the remaining butter and flour to form a paste (this is called a beurre manie).
When the beef is tender, remove the carbonnade from the oven and place it on the stovetop over medium high heat. Add the butter mixture to the carbonnade, stirring constantly until the sauce thickens and becomes velvety.
Taste for seasonings and adjust as necessary. Serve with steamed potatoes or mashed potatoes or over buttered noodles.