Slice the petite sirloin steak very thin against the grain using a sharp knife.
Heat a large non-stick skillet or wok over high heat.
Add 1 tablespoon oil. Add the beef and sear until browned and slightly caramelized. Remove the beef from the skillet and set it aside.
Add the remaining oil and the garlic and cook for 20 seconds until fragrant. Add the red bell peppers, sliced onions and green beans to the skillet and stir fry until soft and caramelized.
Add the beef back to the skillet along with the soy sauce, red curry paste, fish sauce, hoisin sauce, and sugar. Stir to coat the beef and veggies with the sauce.
Add the torn basil and stir until it's just wilted.