Pat the sirloin steak cubes dry with paper towels and toss them with cornstarch until they are evenly coated in a medium bowl.

In a separate small bowl, whisk together the soy sauce, honey, brown sugar, minced garlic, grated ginger, rice vinegar, red pepper flakes, and sesame oil until the mixture is well combined; set aside.

Heat the olive oil in a large skillet or cast-iron pan over medium-high heat until it shimmers, then sear half of the steak cubes for 2-3 minutes per side until browned, and repeat with the remaining steak after removing the first batch.

Return all the seared steak to the pan, whisk the sauce again, and then pour it over the steak.

Bring the mixture to a gentle simmer, stirring constantly for 1-2 minutes, until the sauce thickens and beautifully coats the steak.

Remove the pan from heat immediately, garnish with sesame seeds and chopped green onions, and serve hot.