Cut the chicken breasts into 1 1/2-inch pieces, keeping the shape and size of the chicken pieces as consistent as possible for even cooking
Mix together the marinade ingredients. Add the chicken pieces. Marinate for at least 10 minutes (OR leave in the fridge overnight for even more flavour)
Add the cornstarch and flour to a bowl, whisk together and set aside.
Thinly slice the carrots and spring onions, along with the ginger and garlic and set them aside.
Measure out the sauce ingredients, whisk them together in a bowl, and set aside.
Add the chicken pieces along with the marinade to the bowl with the flour-cornstarch mixture and toss them well to coat completely.
Heat a large skillet or wok over medium-high heat and add the vegetable oil. When the oil is hot, add in the chicken so the bottom of the pan is covered but not overcrowded. You may have to cook the chicken pieces in 2 batches, depending on the size of your pan.
Flip the chicken pieces once they start to brown.
When the chicken pieces are browned on both sides and the internal temperature measures 74 degrees Celsius (165 Fahrenheit), remove them to a plate lined with paper towel and repeat with the remaining chicken.
Once all the chicken is cooked, discard the vegetable oil and wipe the pan.
Add the sesame oil to the skillet or wok and heat up over medium-high heat. Add the garlic and ginger and cook just until fragrant. Add the chopped veggies (save some green onions for garnish) to the skillet and sauté for just a few moments until the carrots and onions start to brown slightly and soften just a little bit.
Whisk the sauce ingredients together one more time (because the cornstarch tends to settle). Add the sauce ingredients into the hot pan with the veggies. Cook until the sauce thickens.
Add the chicken pieces back in and toss everything together with the sesame seeds. Serve over rice with green onions and more sesame seeds for garnish (if desired).