Ultimate Slow Cooker Mongolian Beef

My brother in law called me at 7pm on a Tuesday, frantic because he had promised to make dinner for my sister and completely forgot until he walked through the door. I talked him through this exact recipe while he hovered over his phone in the kitchen, and when I got the text at 9pm with an empty slow cooker and three thumbs up emojis, I knew this one was a keeper for anyone who needs a miracle meal with zero stress.

Last winter during a snowstorm that trapped us inside for three days straight, this slow cooker beef became the anchor that held my household together. The smell would waft through the house every few hours, and somehow knowing something delicious was bubbling away in the corner made the cabin fever feel almost cozy instead of claustrophobic.

Ingredients

• 2 pounds flank steak, thinly sliced against the grain: Cutting against the grain is not optional here, I learned the hard way that slicing with the grain gives you chewy strings instead of tender ribbons that practically melt in your mouth
• 3/4 cup low-sodium soy sauce or tamari: Regular soy sauce made my first batch overwhelmingly salty, so stick with low-sodium to let the other flavors shine through without overwhelming your palate
• 2/3 cup brown sugar, packed: Dark brown sugar adds a deeper molasses flavor that really complements the hoisin, though light brown works perfectly fine if that is what you have in your pantry
• 1/2 cup hoisin sauce: This Chinese condiment is the secret ingredient that gives restaurant quality depth, and once you buy a bottle, you will find yourself putting it on everything from chicken to roasted vegetables
• 4 cloves garlic, minced: Fresh garlic is absolutely worth the effort here, as garlic powder cannot replicate that mellow sweetness that develops during slow cooking

Instructions

Get your slow cooker ready:

Spray the inside lightly with cooking spray because no matter how good the food tastes, soaking a slow cooker for three hours afterward is nobody's idea of a good time.

Layer in the beef:

Arrange your steak slices in the bottom of the cooker, and do not worry if some pieces overlap, they will shrink down significantly as they cook.

Whisk up the magic sauce:

Combine the soy sauce, brown sugar, hoisin, and garlic in a bowl, whisking until most of the sugar crystals disappear into the dark amber liquid.

Coat and cook:

Pour that gorgeous sauce over the beef and give everything a good toss so every slice gets covered, then set it to low and let it work its magic for 4 hours.

The final stir:

About halfway through cooking, open the lid and give everything a stir to redistribute the sauce that has settled at the bottom.

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This recipe became my go to for new parents and families dealing with illness because the leftovers reheat beautifully and somehow taste even better the next day when the flavors have had extra time to meld together in the refrigerator.

Making It Thicker

If you prefer a restaurant style thick sauce that clings to every bite of beef, mix 2 tablespoons of cornstarch with 2 tablespoons of cold water until smooth and stir it in during the last 30 minutes of cooking. The sauce will transform from thin and glossy into a rich coating that feels professional and finished.

Serving Suggestions

While this beef is fantastic on its own, serving it over steamed jasmine rice creates that perfect texture contrast between tender meat and fluffy grains. Fresh steamed broccoli or snow peas add a bright crunch that cuts through the richness, and a sprinkle of sliced green onions on top makes the whole bowl look like something from a takeout menu.

Customizing The Heat Level

My family is divided on spice tolerance, so I started serving red pepper flakes on the side instead of adding them directly to the slow cooker. This way everyone can customize their own bowl, from no heat at all to as spicy as they dare.

• Slice your beef when it is slightly frozen for cleaner, easier cuts
• Double the sauce ingredients if you love extra sauce for your rice
• Cornstarch thickening happens fast once you add it, so stir constantly for that last 30 minutes

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There is something profoundly satisfying about a meal that delivers restaurant quality results with essentially zero active cooking time. This recipe has saved my dinner plans more times than I can count.

Recipe FAQs

→ Can I use a different cut of beef?

Yes, you can use sirloin or ribeye instead of flank steak. For best results, slice against the grain and ensure the meat is thinly cut. Cooking times may vary slightly depending on the thickness and cut of beef.

→ How can I make the sauce thicker?

To thicken the sauce, dissolve 2 tablespoons cornstarch in 2 tablespoons cold water and stir into the slow cooker during the last 30 minutes of cooking. This creates a beautiful, glossy coating for the beef.

→ Is this dish gluten-free?

Yes, when using tamari or gluten-free soy sauce and ensuring your hoisin sauce is gluten-free. Always check ingredient labels as some hoisin sauces may contain wheat or other gluten-containing ingredients.

→ Can I prepare this ahead of time?

Absolutely! You can assemble the dish the night before and refrigerate. In the morning, simply transfer to the slow cooker and cook as directed. The flavors will meld beautifully during cooking.

→ What sides pair well with this dish?

This dish pairs wonderfully with jasmine rice, steamed broccoli, or sautéed bok choy. The rich sauce complements these sides perfectly and creates a balanced, satisfying meal.