Cover and cook on LOW for 8 hours, or until the beef is tender and easy to pull apart with a fork.
Remove the bay leaf and thyme. Stir in the sour cream and heavy cream.
7 ounces sour cream, 3 tablespoons heavy cream
Add the cold butter and stir until the sauce is smooth and glossy. Do not boil the sauce after adding the dairy. Keep it warm. Serve over egg noodles.
1 tablespoon butter, 1 pound egg noodles
NOTES
1. Can I skip the cognac? Yes. Replace it with more beef broth. The sauce will lose a little depth, but it will still taste good.2. Why add the sour cream at the end? Sour cream can break if it boils. Stir it in after the beef is done and keep the heat low.3. What if my sauce seems thin? Serve it over egg noodles, which soak up extra sauce well. You can also let the sauce sit on warm for a few minutes with the lid slightly open.4. How do I know the beef is done? It should press apart easily with a fork. If it still feels firm, give it more time. 5. Storage
Refrigerator: Store covered in the fridge for up to 3 days.