Sour Cream Portobello Flank Steak Crockpot Recipe

This slow cooker dinner is the definition of set-it-and-forget-it. Thinly sliced flank steak, meaty portobello caps, and sweet shallots simmer low and slow in a velvety sour cream and brown gravy sauce until the beef is fork-tender.

Serve it over buttered egg noodles for a comforting meal that tastes like it took hours of hands-on work — but really, it's just a few minutes of layering ingredients.

This recipe turns a handful of everyday ingredients into a rich, savory stroganoff-style dinner. The slow cooker does all the heavy lifting: flank steak strips become melt-in-your-mouth tender, mushrooms soak up the gravy, and shallots turn sweet and jammy.

The sour cream and brown gravy mix create a silky, deeply flavored sauce with zero stirring. Just dump everything into the crockpot, walk away, and come back to a bubbling, aromatic meal that's ready to serve over noodles.

Ingredients

Why this recipe works

Flank steak is a lean, flavorful cut that benefits from long, slow cooking. When sliced thinly against the grain and cooked on low, it breaks down into tender, shreddable pieces rather than becoming tough and chewy.

The slow, moist heat of the crockpot allows the connective tissue to melt, turning the beef into velvety strands that soak up the sauce.

The combination of sour cream and brown gravy mix is a clever shortcut that yields a rich, glossy sauce without any roux-making or constant whisking.

The sour cream adds tang and creaminess, while the gravy mix provides deep umami and a savory backbone. As the mixture simmers, it thickens naturally, coating every piece of beef and mushroom in a luxurious, silky gravy.

Notes and substitutions

For the best texture, slice the flank steak thinly against the grain. This means cutting across the lines of the meat fibers, which shortens them and makes the meat more tender. If the steak is partially frozen, it's easier to slice thinly. You can ask the butcher to slice it for you, or use a sharp chef's knife at home.

Portobello mushrooms add a meaty, earthy flavor that pairs beautifully with the beef. Choose caps that are firm and dry, and wipe them clean with a paper towel rather than rinsing them under water. Shallots are milder and sweeter than onions, but if you don't have them, a small yellow onion cut into wedges works just as well.

• flank steak: sirloin steak or chuck roast, thinly sliced
• portobello mushrooms: cremini or white button mushrooms
• shallots: 1 small yellow onion, peeled and quartered
• brown gravy mix: 1 tablespoon all-purpose flour plus 1 teaspoon beef bouillon powder

Equipment

• 6-quart slow cooker
• Cutting board
• Chef's knife
• Measuring cups and spoons
• Serving spoon