Heat a skillet over medium-high heat and add in the canola oil. Toss the steak strips in 2 tbsp cornstarch and cook in the hot oil in batches, searing the steak on each side for about 30 seconds. Remove to a plate and keep warm.
Combine the soy sauce, brown sugar, hoisin, water and 1 tbsp cornstarch in a small bowl and whisk till combined.
Reduce heat to medium and add the garlic to the pan and cook until fragrant, about 30 seconds. Pour in the sauce mixture and cook until sauce begins to thicken. Add the steak back into the sauce and season with red pepper flakes, black pepper and the green onions. Serve hot over hot rice and enjoy!