Spicy stir-fried chicken (Dak-galbi)

Sauce:

12 garlic cloves, minced
1 teaspoon peeled and minced ginger
2 tablespoons soy sauce
½ cup water
⅓ cup gochu-garu (Korean hot pepper flakes)
2 tablespoons rice syrup (or corn syrup, or sugar)
½ teaspoon ground black pepper