Vietnamese Sweet Potato and Shrimp Tempura

INGREDIENTS

1/4 cup

rice flour , freshly ground

2 cups

all-purpose flour

1/2 cup

corn starch

1 tbsp

baking powder

1 tsp

sugar

1/2 tsp

turmeric powder

3 1/2 tsp

salt

1 tsp

black pepper , freshly ground

1 tsp

cayenne powder

2 2/3

to 3 cups seltzer water (see tips)

8 oz

crushed ice , (1-1/2 cups)

2 lb

large shrimp

2 cloves

garlic , finely minced

sweet potatoes

1 qt

peanut oil (or regular vegetable oil) , for deep frying, as needed