How to Make It
In a baking dish, whisk the mirin, soy, lime juice, clementine juice and 1/4 cup of water. Add the tofu and turn to coat. Refrigerate for 2 to 4 hours, turning once; pat dry.
In a saucepan, heat the vegetable oil. Cook the onion and garlic over moderate heat, stirring, until the onion starts to brown. Add dark brown sugar, black plums and tamarind paste. Cook, stirring, until soft, about 12 minutes; let cool. Transfer sauce to a blender and pulse with Sriracha until nearly smooth. Season with salt and set aside.
In a shallow dish, spread 1 cup of the rice flour. In another shallow dish, whisk the eggs with the milk and the remaining 2 cups of rice flour. Spread the panko in a third shallow dish. Dredge the tofu in the flour, the egg mixture and then the panko, lightly patting the coating to help it adhere.
In a large saucepan, heat 1 1/2 inches of oil to 325°. Fry the coated tofu in batches, turning, until deep golden, 7 minutes. Transfer to paper towels to drain and season with salt. Serve hot, with the Plum Sauce.