For the stir-fry sauce, whisk together cornstarch and water in a medium-sized bowl. Add remaining sauce ingredients. Set aside.
Add 2 Tbsp. olive oil to a large skillet or wok and heat over medium-high heat. Add chicken to skillet. Cook for 3 to 5 minutes.
Beat eggs well; add milk and vanilla.
In a separate bowl, combine rice flour, tapioca starch, potato starch, sugar, and salt. Add to egg mixture and whisk until smooth.