Heat oil to 325 degrees F.
Cut mushrooms crosswise into 3/8-inch thick slices. Lightly dust them with 2 tablespoons flour; set aside. In a medium bowl, whisk together flour, club soda, eggs, and coarse salt to form a batter.
Dip portobello fries into batter. Blanch fries in hot oil. Drain on a paper towel-lined baking sheet. Let cool. Heat oil to 375 degrees F. Cook the blanched fries in hot oil until golden brown and crispy. Drain on a paper towel-lined baking sheet. Season with sea salt, and serve with ponzu sauce.
1 teaspoon soy sauce
3 tablespoons ketjap manis
1 teaspoon Thai fish sauce
6 tablespoons mirin
2 teaspoons rice wine vinegar
2 (1/8-inch) thick slice ginger, smashed
In a small bowl, combine soy sauce, ketjap manis, fish sauce, mirin, and rice wine vinegar. Add ginger. Cover, and let stand overnight, refrigerated. Strain through a fine sieve.
Yield: about 2/3 cup