Season the steak(s) with salt and pepper and seal them in a vacuum seal bag.
Cook for 36 hours in the water bath.
Remove and place steaks on a plate, reserving the bag sauce to make the mushroom gravy. Thoroughly pat them dry so the outside is very dry.
**if not serving right away, place the bag in an ice bath for 10 minutes after removing from the water bath. Store in the fridge or freezer until ready to use.
Heat oil in a cast iron skillet over high heat until smoking.
Add the steak and brown for 30-60 seconds on each side. Remove and serve with mushroom gravy.
How to Make Mushroom Gravy
Heat the butter in a skillet and add the shallots, thyme and mushrooms. Sauté about 5-7 minutes, or until mushrooms have lost much of their liquid and pan starts to dry out.
Add the brandy and cook for 3-5 minutes, until most of it has cooked off.
Add all the remaining ingredients (except the heavy cream) and bring to a simmer. Cook for 2-3 minutes.
Add the cream and simmer for about 3-5 minutes, until thickened slightly. If it is still too thin, keep cooking until it is thick enough to coat the back of a spoon.
Add additional salt if needed, then serve over chuck steak.
Notes
If the gravy is too thin, continue simmering until it thickens. It should be thick enough to coat the back of a spoon.
If gravy is too thick, add additional beef stock until you reach your desired consistency. Adjust the seasoning if needed.
It may be tempting to add butter to the bag when cooking your steak, but butter actually takes flavor away from the meat! It's better to add butter during the searing process.
Be sure to reserve the cooking liquid from the bag for the mushroom gravy.
If you're not serving right away, place the bag in an ice bath for 10 minutes after removing from the water bath. Store in the fridge or freezer until ready to use.
Refer to the temperature chart in the post for additional cooking options.
If you buy a chuck roast, cut it into 1 ½ to 2" steaks to sous vide.