Season beef cubes with salt and pepper, then dredge with flour, removing any excess.

Melt 2 tablespoons of butter in a large skillet over high heat. Brown beef cubes in batches, adding 1 tablespoon of butter if needed. Transfer browned beef to a Dutch oven.

Melt remaining 1 tablespoon butter in the skillet over medium heat. Cook sliced onions, stirring occasionally, until browned (about 15 minutes). Combine browned onions with the beef in the Dutch oven.

Deglaze the skillet with the Belgian beer, scraping up any browned bits. Bring to a boil, then pour over the meat in the Dutch oven.

Add fresh thyme sprigs and bay leaves to the Dutch oven.

Simmer, covered, over low heat for 1.5 to 2 hours, or until the beef is very tender.

Before serving, stir in the red currant jelly and vinegar. Simmer for 5 minutes.

Remove thyme sprigs and bay leaves before serving.

Taste and adjust seasoning to preference before serving.