In a large bowl, whisk together flour, cornstarch, rice flour, salt, turmeric, and black pepper. Crumble in the bouillon cube and whisk again to break it up. Whisk in the sparkling water and cold water until smooth. The batter should be slightly thick, similar to pancake batter but thinner. Set aside and let rest for at least 30 minutes.
1 ½ cups all-purpose flour, ½ cup cornstarch, ½ cup rice flour, 1 teaspoon salt, ½ bouillon cube, ½ teaspoon turmeric, ¼ teaspoon black pepper, 1 cup sparkling water, ¾ cup cold water