Dinner · Part 3 of 3: Tips & recipe card

Slow Cooker Sour Cream Mushroom Flank Steak Tips, FAQ & printable recipe

Name: Slow Cooker Sour Cream Mushroom Flank Steak
Prep time: 10 min
Cook time: 6 h
Total time: 6 h 10 min
Cuisine: American
Ingredients: 2 lb flank steak, thinly sliced against the grain; 1 can (10.5 oz) condensed cream of mushroom soup; 1 cup diced white onion; 1 cup sour cream; 1 oz brown gravy mix (1 envelope); 8 oz sliced mushrooms; 12 oz wide egg noodles, cooked for serving; 2 tbsp butter, for noodles

By Clara Weller · Oct 28, 2026

Slow cooker flank steak in creamy mushroom gravy with onions

Prep: 10 min
Cook: 6 h
Total: 6 h 10 min
Serves: 6

Tips for success

For the most tender flank steak, slice it as thinly as you can against the grain. If you have time, freeze the steak for 15-20 minutes before slicing — it makes cutting easier.

Also, don't skip the rest time after cooking; it lets the juices redistribute, keeping the meat moist. If you prefer a thicker gravy, remove the lid for the last 30 minutes of cooking to let some liquid evaporate.

The beauty of this recipe is its simplicity. You can prep the ingredients the night before and store them in the refrigerator in the slow cooker insert. In the morning, just put the insert in the base and turn it on.

This makes it perfect for busy mornings. For a richer flavor, sauté the onions and mushrooms in butter before adding them to the slow cooker — it adds an extra layer of depth, though the dump-and-go version is just as delicious.

Variations

Add Mushrooms: Stir in 8 oz of sliced cremini or button mushrooms along with the onions for extra earthy flavor and texture. They'll soften and absorb the gravy beautifully. If you prefer a chunkier mushroom presence, sauté them first and add them during the last hour of cooking.
Use Chicken: Swap the flank steak for boneless, skinless chicken thighs or breasts. Cook on low for 4-5 hours, or until the chicken reaches 165°F (74°C). Shred or slice before serving. This version is lighter but just as creamy and satisfying.
Make It Spicy: Add a teaspoon of hot sauce or a pinch of red pepper flakes along with the gravy mix for a subtle kick. You can also use a spicy brown gravy mix if you can find one. This gives the dish a gentle warmth without overpowering the creamy sauce.
Vegetarian Version: Replace the beef with a bag of frozen meatless meatballs or a can of drained chickpeas. Use a vegetarian cream of mushroom soup and a vegetarian brown gravy mix. Cook on low for 4 hours, then stir in the sour cream. Serve over noodles as a hearty meatless dinner.

Storage and make-ahead

Fridge: Store in an airtight container in the fridge for up to 4 days. The sauce may thicken; add a splash of broth or water when reheating.
Freezer: Freeze the cooked and cooled beef and gravy in a freezer-safe container for up to 3 months. Thaw overnight in the fridge and reheat gently.
Reheat: Reheat in a saucepan over medium-low heat, stirring occasionally, until hot and bubbly. Add a little beef broth or water if needed to loosen the sauce.

Store leftovers in an airtight container in the refrigerator for up to 4 days. The flavors will continue to meld, making it even tastier the next day.

Reheat gently on the stovetop or in the microwave, adding a splash of beef broth or water if the sauce has thickened too much. The beef can be shredded and used in sandwiches, over mashed potatoes, or stirred into pasta.

This recipe is ideal for meal prep. Assemble everything in the slow cooker insert the night before, cover, and refrigerate. In the morning, simply place the insert into the slow cooker base and cook on low.

You can also cook the full recipe, let it cool, and store it in the fridge for up to 4 days. Reheat portions as needed for quick lunches or dinners.

Serving ideas

Serve this sour cream mushroom flank steak over a bed of warm, buttered egg noodles. The wide noodles are perfect for catching the creamy gravy. For a lighter option, serve over mashed potatoes, rice, or even creamy polenta. A side of steamed green beans or a crisp green salad adds a fresh contrast to the rich sauce.

Garnish with a sprinkle of fresh parsley or chives if you like, though it's delicious as is. The dish is hearty enough to be a complete meal on its own, but it also pairs well with crusty bread for soaking up every last drop of sauce. For a family-style dinner, bring the slow cooker to the table and let everyone serve themselves.

Frequently asked questions

Can this recipe be made ahead of time?

Yes, you can assemble the raw ingredients in the slow cooker insert the night before and store it in the refrigerator. In the morning, place the insert in the slow cooker base and cook as directed. You can also cook the entire recipe, cool it, and refrigerate for up to 4 days. Reheat gently on the stovetop or microwave.

Why does the sour cream sometimes curdle?

Curdling can happen if the slow cooker is on high heat or if the sour cream is added too early and boils. To avoid this, use full-fat sour cream and stir it in during the last 30 minutes of cooking, or follow the recipe as written — dolloping it on top and letting it melt slowly on low heat usually prevents curdling.

Can this recipe be frozen?

Yes, the cooked beef and gravy freeze well for up to 3 months. Let it cool completely, transfer to a freezer-safe container, and freeze. Thaw overnight in the refrigerator and reheat gently on the stovetop or in the microwave. The texture of the sauce may change slightly, but it will still be delicious.

What can be used instead of cream of mushroom soup?

If you don't have cream of mushroom soup, you can use cream of chicken soup or a homemade white sauce. For a dairy-free option, use a dairy-free cream soup alternative or make a roux with dairy-free butter and flour, then whisk in broth and milk. Adjust the seasoning to taste.

How can the gravy be thickened if it's too thin?

If the gravy is too thin at the end of cooking, mix 1 tablespoon of cornstarch with 2 tablespoons of cold water to make a slurry. Stir it into the slow cooker and cook on high for 15-20 minutes until thickened. Alternatively, remove the lid and cook on high for 30 minutes to let some liquid evaporate.

Recipe card

Slow Cooker Sour Cream Mushroom Flank Steak

Prep 10 minCook 6 hTotal 6 h 10 minServes 6

Ingredients

2 lb flank steak, thinly sliced against the grain
1 can (10.5 oz) condensed cream of mushroom soup
1 cup diced white onion
1 cup sour cream
1 oz brown gravy mix (1 envelope)
8 oz sliced mushrooms
12 oz wide egg noodles, cooked for serving
2 tbsp butter, for noodles

Instructions

Place the sliced flank steak in the bottom of a 6-quart slow cooker. Spread the cream of mushroom soup over the beef, then scatter the diced onions on top. Add the sliced mushrooms if using. Sprinkle the brown gravy mix evenly over everything.
Dollop the sour cream over the top of the mixture. Do not stir; just leave it in spoonfuls. The sour cream will melt into the gravy during cooking, creating a rich, creamy sauce.
Cover and cook on LOW for 6 to 8 hours, or on HIGH for 3 to 4 hours, until the beef is fork-tender and easily shreds. The sauce will be bubbling and thickened. Stir gently before serving. Let it rest for 3 minutes before slicing.
Turn off the slow cooker and let the beef rest in the sauce for at least 3 minutes before serving. This allows the juices to redistribute and the meat to stay moist.
While the beef rests, cook the wide egg noodles in a large pot of salted boiling water according to package directions. Drain and toss with butter. Serve the beef and gravy over the buttered noodles.

Contains: gluten, milk, eggs

Estimated nutrition per serving

Calories: 520
Protein: 35 g
Carbohydrates: 30 g
Fat: 28 g

Automatic estimate from the ingredient list, not laboratory-verified.

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This recipe is based on a short cooking video and is published under the pen name Clara Weller. It was checked before publication, but errors can slip through. Nutrition, when shown, is an estimate. Read more in our editorial policy and on our food safety page.