Green Bean and Shiitake Tempura with Ponzu Mayonnaise Recipe

Name: Green Bean and Shiitake Tempura with Ponzu Mayonnaise Recipe
Ingredients: For the Ponzu Mayonnaise:; 1 large egg yolk; 1 tablespoon red or white miso paste; 1 tablespoon ponzu sauce (see note above); 1 tablespoon honey; 1 cup vegetable oil; Kosher salt; For the Tempura:; 1 1/2 quarts peanut oil; 1 cup unbleached all-purpose flour; 1/2 cup rice flour (or cornstarch); 1 egg; 1 1/2 cups ice cold seltzer water; 1/2 pound green beens, trimmed; 4 ounces (about 8 medium) shiitake mushrooms, stems removed, caps cut in half