Preheat your oven to 325°F (165°C).
Place the beef chuck, carrots, onion, potato, and mushrooms into a large roasting pan or Dutch oven.
Pour the water or broth into the bottom of the pan, just enough to cover it.
Season generously with salt and pepper.
Cover the pan tightly with a lid or heavy-duty foil and cook for 4 hours.
Remove the cover and continue to cook for 1 more hour, allowing the meat and vegetables to brown nicely.
Remove the roast from the oven.
Before seasoning the main dish further, use a gram scale to carefully weigh out your keto portion: 23 g (0.81 oz) of cooked beef and 12 g (0.42 oz) of cooked carrots.
Season the remaining pot roast in the pan to your family's preference with additional herbs, spices, or salt.
To complete your keto meal, place your weighed beef and carrots in a small dish and top with the butter, allowing it to melt over the warm food.
Mix the heavy cream with a small amount of water to create a keto-friendly “milk” to drink.
Serve the walnut oil in a small cup to drink alongside your meal.