Ultimate Slow Cooker Mongolian

The way my apartment building smells when someone makes Mongolian beef should be illegal. I first attempted this recipe during a particularly brutal February when comfort food was the only thing keeping me sane. My tiny slow cooker sat on the counter, bubbling away with that impossible combination of soy, ginger, and something sweet that makes your stomach growl from three rooms away. Now it is the one dish my friends actually request by name.

Last summer I made this for a backyard dinner and watched my cousin who claims to hate beef polish off three servings. The trick is slicing against the grain which sounds technical but makes all the difference between chewy and melt in your mouth. Now I keep flank steak in the freezer specifically for those nights when I need something that feels like a hug in food form.

Ingredients

• 2 pounds flank steak: Slicing this thin against the grain transforms it into something supremely tender
• 3/4 cup low-sodium soy sauce: Regular soy sauce will make this too salty so stick with low-sodium
• 3/4 cup brown sugar: This creates that characteristic Mongolian beef sweetness we all love
• 1/2 cup water: Helps balance the intense flavors and creates enough sauce
• 1/4 cup hoisin sauce: Adds that deep umami richness that makes restaurant versions so addictive
• 1 tablespoon sesame oil: A little goes a long way for that authentic finish
• 4 cloves garlic: Fresh minced garlic is non-negotiable here
• 1 tablespoon fresh ginger: Grated fresh ginger brings brightness that ground ginger cannot match
• 1/2 teaspoon crushed red pepper flakes: Optional but highly recommended for a gentle heat
• 1/4 cup cornstarch: Half coats the beef half thickens the sauce at the end
• 1/4 cup cold water: Mixed with cornstarch to create the slurry
• 4 green onions: Fresh garnish adds color and a mild onion bite
• 1 tablespoon toasted sesame seeds: For that restaurant-style finish

Instructions

Mix the sauce:

Whisk together soy sauce, brown sugar, water, hoisin sauce, sesame oil, garlic, ginger, and red pepper flakes until the sugar dissolves completely.

Coat the beef:

Toss the sliced flank steak with half the cornstarch in a zip-top bag until every piece is lightly dusted.

Start the slow cooker:

Transfer the coated beef to your slow cooker and pour the sauce over everything, stirring so the beef is fully submerged.

Let it cook:

Cover and cook on low for 4 hours until the beef is fork tender and the sauce has darkened to a rich mahogany color.

Thicken the sauce:

Whisk the remaining cornstarch with cold water until smooth, stir it into the slow cooker, and cook for 30 more minutes.

Serve it up:

Spoon over steamed rice and top with green onions and sesame seeds while the beef is still hot.

Save Pin

This recipe saved me during finals week when cooking anything requiring actual attention was out of the question. My roommate came home to that aroma and immediately asked if we could have it every Tuesday. Some foods are just like that.

Making It Your Own

I have added sliced bell peppers and carrots during the last hour of cooking when I needed to stretch the meal for unexpected guests. The vegetables absorb all that sauce and become something special entirely.

Serving Ideas

Steamed jasmine rice is classic but this also works over cauliflower rice if you are watching carbs. The sauce clings beautifully to cauliflower florets which cook faster than you would expect.

Storage and Meal Prep

This actually tastes better the next day when the flavors have had time to really meld together. I pack it in glass containers and reheat gently with a splash of water to loosen the sauce.

• Fridge up to 4 days in airtight containers
• Freeze for up to 3 months without the garnish
• Reheat on the stove over medium-low heat

Save Pin

There is something profoundly satisfying about a meal that tastes like you spent hours hovering over it when really you were just living your life.

Recipe Questions & Answers

→ How do I ensure the beef stays tender?

Slicing the flank steak thinly against the grain and slow cooking it for several hours allows the meat fibers to break down, yielding tender, juicy beef.

→ Can I adjust the sweetness of the sauce?

Yes, reducing the amount of brown sugar will tone down the sweetness to your preference without sacrificing the overall balance.

→ What can I substitute for soy sauce for gluten-free needs?

Using tamari instead of soy sauce provides a gluten-free alternative that maintains the umami flavor.

→ How is the sauce thickened at the end?

A slurry made of cornstarch and cold water is stirred in during the last 30 minutes, creating a glossy, thick sauce that clings beautifully to the beef.

→ What are good side options for this dish?

Steamed jasmine or basmati rice pairs well, and for a low-carb option, steamed broccoli or noodles complement the flavors nicely.

→ Can I add vegetables to the dish?

Yes, adding sliced carrots or bell peppers during cooking adds color, nutrition, and a slight sweetness that enhances the overall taste.