In a small bowl, add chicken stock, soy sauce, sugar, vinegar and cornstarch. Whisk and set aside.
Preheat large skillet on medium-high heat, add oil and chicken. Sprinkle it with salt and pepper and cook for 10 minutes or until seared and cooked through, stirring a few times but not too often.
Add asparagus and cook for another 2-3 minutes. Add garlic and ginger, and stir fry for another 30 seconds.
Give stir fry sauce a whisk, pour over chicken and asparagus and bring to a simmer. Cook for 1-2 minutes or until sauce has thickened, stirring a few times.
Garnish with sesame seeds and serve.
Notes
Store: Store leftovers in an airtight container in the fridge for up to 3 days.Reheat: Reheat in a microwave or on the stove with a bit of water or broth until heated through.Freeze: Chicken does freeze well but not the asparagus.