Whisk the hoisin sauce, fresh squeezed orange juice, and reduced sodium soy sauce together to make the marinade. Add the sirloin steaks to the marinade, turn to coat, cover, and refrigerate for 2 hours.
While the steaks are marinating, bring a large pot of water to a boil and prepare an ice bath (a bowl of ice and cold water).
Place the broccoli florets in a wire basket or directly into the boiling water and blanch at a slow boil for 3 to 4 minutes. Immediately transfer the florets to the ice bath to stop the cooking; let sit until chilled, then drain and set aside.
About 5 minutes before cooking, remove the steaks from the refrigerator to come toward room temperature. Remove the steaks from the marinade and reserve the marinade for the sauce.
Heat a medium nonstick sauté pan over high heat until hot. Spray the pan with cooking spray, add the steaks, and cook 3 minutes on each side for medium-rare. Transfer the steaks to a cutting board to rest while you finish the sauce and vegetables.
Pour the reserved marinade into the same skillet used for the steaks. Reduce heat to medium-low, bring to a boil, and simmer 2 to 3 minutes.
While the marinade is simmering, heat a large nonstick skillet over high heat and add the aji sesame oil. Add the julienned white onion, minced garlic, and minced fresh ginger and cook 1 to 2 minutes, stirring, until fragrant and the onion begins to soften.
Add the spiralized broccoli stems (broccoli noodles) to the skillet with the aromatics and cook, stirring, for about 3 minutes until tender-crisp.
Add the blanched broccoli florets to the skillet and cook until hot.
Divide the broccoli noodles and florets between two plates. Slice the rested steaks into thin strips, arrange the steak on top of the noodles, spoon the cooked marinade sauce over everything, and serve.