Season the beef with salt, pepper, a little garlic powder and put in a vacuum bag. Process in the water bath at 56C (133 F) for 48 hours (36 is probably fine).
Pan fry the meat, briefly, on relatively high heat to brown the meat. Remove to a plate, and deglaze the pan with the half bottle of Goudenband. Reduce to a couple tablespoons, and add the beef stock. Reduce till slightly thickened. Stir in butter, a tablespoon at a time. Keep moving the butter around the pan to emulsify. Serve sauce over beef.