Warm the oil in a large skillet over medium high heat. Brown the beef until cooked through, crumbling it as it browns. Drain thoroughly, then add the garlic and ginger and cook another minute or two until fragrant.
Whisk together the brown sugar, cornstarch, soy sauce, and chili paste. Pour the liquids over the beef, stir to combine, and bring to a simmer for 2 minutes to blend the flavors and slightly thicken the sauce.
Add the peas, stir and simmer a minute longer. The peas will thaw and warm in the hot skillet. Sprinkle with green onions before serving.
Notes
This dish reheats wonderfully. I've learned to double the recipe every time I make it. The beef freezes well too, just skip the green onions and sprinkle them on the top when ready to serve. Cheater Korean Beef is pretty much the ultimate in flavorful and frugal make-ahead meals.A note about fresh ginger: My first choice when making this recipe is to slice the ginger into tiny matchsticks for the best taste and texture combination. However, when I only have frozen ginger on hand, or when I simply don't have an extra minute to slice it, it works beautifully to simply grate the ginger on a microplane.