• Step 1: Heat the olive oil in a large skillet or wok over high heat. Add the cubed beef and cook, stirring occasionally, until the beef is browned on all sides, about 3-4 minutes.
• Step 2: Add the minced garlic and diced onion to the skillet. Sauté for an additional 2-3 minutes, or until the onion is translucent and fragrant.
• Step 3: In a small bowl, whisk together the soy sauce, fish sauce, brown sugar, and black pepper. Pour the sauce mixture into the skillet and toss the beef and vegetables to coat evenly.
• Step 4: Continue cooking for 2-3 minutes, shaking or tossing the skillet frequently, until the sauce has thickened and the beef is cooked through.
• Step 5: Remove the skillet from heat and stir in the chopped cilantro, if using. Serve immediately over steamed rice.