Orange Chicken Sandwich

4 chicken cutlets, thighs, or breasts
2 cups buttermilk
1/4 cup flour
1 Tbsp chili powder
1 Tbsp garlic powder
1 Tbsp sazon or salt
1 Tbsp onion powder

Dry batter:
1.5 cup potato starch
1.5 cup rice flour
1 Tbsp chili powder
1 tbsp garlic powder
1.5 tbsp sazon
1 tbsp onion powder
1-2 tsp MSG

Sauce:
2 tbsp butter
4-5 cloves garlic
2 tbsp ginger
2 tsp chili flakes
1/4 cup rice vinegar
1 cup soy sauce
zest and juice of 2 oranges
2 tsp corn starch (1/4 cup water)
1/4 cup honey

4 potato buns
Kimchi and kewpie Mayo