Place fresh or frozen chicken breasts in your pressure cooker.
Mix garlic, onion, honey, soy sauce, vinegar, ginger, and pepper in a bowl and pour over the chicken.
Place the lid on the pressure cooker, seal the valve and hit 'Poultry'.
Make sure your timer is on 'manual' and set for 18 minutes.
Once done, release the pressure valve manually and remove chicken. You can either shred or chop the chicken. Set aside.
Once you've finished the chicken, you'll have the liquid from the chicken still in the pressure cooker. With the lid off, hit 'sauté' and bring the sauce to a simmer/boil.
Mix 1/4 cup cold water with 3 Tbsp. cornstarch in a small bowl and add to the bubbling liquid.
Stir until thickened. Add shredded/chopped chicken back to the pot to keep warm.
Serve over rice and sprinkle with scallions and sesame seeds (optional)