Preheat oven to 350 degrees.
In a small sauce pan, combine the tamari, lemon juice, rice wine, garlic, ginger, and agave syrup, and bring to a boil.
Mix the cornstarch with a tablespoon of water in a separate bowl. Then pour into the boiling tamari mixture. Bring mixture to a boil once again, and then lower to a simmer for 2-3 minutes until it becomes thick. Remove from heat.
Put 2 tablespoons of the thickened tamari mixture to the side. Using a basting brush or the back of a spoon, spread the rest of the mixture on the top of the chicken and place in a glass baking dish.
Place the chicken into the oven and cook for 15-20 minutes.
Sprinkle the scallions and sesame seeds on top of the chicken and cook 2-3 more minutes under the broiler.
Serve immediately with the remaining teriyaki sauce on the side.