In a large bowl, combine the batter ingredients, whisking until frothy and well combined. Add the chicken and set in the fridge for 20 minutes.
Meanwhile, add the sauce ingredients to a small saucepan over medium heat and whisk until incorporated. Taste and season accordingly.
Reduce heat to low and cover, stirring occasionally. Heat oil in a skillet and fry the chicken until golden brown. Toss with the sauce and serve with red pepper flakes if desired.
