In a mixing bowl, whisk together soy sauce, brown sugar, rice vinegar, sesame oil, mirin, ginger, garlic, black pepper, and red pepper flakes
Place the chopped beef in the crockpot and pour the sauce over it. Stir to coat the beef evenly
Cook on low for 6-8 hours or on high for 3-4 hours
In a small bowl, whisk together cornstarch and water to make a slurry
About 30 minutes before serving, add the cornstarch slurry to the crockpot and stir to thicken the sauce
Garnish with chopped green onions and sesame seeds. Best served with white rice
Notes
Sear it: Before you throw it in the crockpot, try giving the beef a quick sear in a hot pan. This will help lock in those delicious flavors
Keep it consistent: Make sure to cut the beef into pieces that are about the same size so they cook evenly
Spice it up: If you like things spicy, you can crank up the heat by adding some extra red pepper flakes or hot sauce. If you're not a fan of spicy food, you can tone things down by using less red pepper flakes or leaving them out altogether.
Add some veggies: Don't be afraid to throw in some sliced onions, bell peppers, or shaved carrots into the mix
Use low-sodium soy sauce: To cut down on the salt content, try using low-sodium soy sauce
Thicken up the sauce: If you like your sauce a bit thicker mix a tablespoon of cornstarch with some water and stir it into the slow cooker during the last 30 minutes of cooking.
Serve it up: This dish is perfect served over rice or noodles, which will soak up all that delicious sauce
Prep ahead of time: You can get a head start on this recipe by starting the sauce and cutting up the meat ahead of time. This will save you some time on the day of cooking
Save: this is a big batch so if you don't eat it all you can always freeze and save for a later date