How to Make It
In a small bowl, cover the raisins with water and let stand until plumped, about 30 minutes. Drain the raisins, reserving 2 tablespoons of the soaking liquid.
Meanwhile, in a medium saucepan, heat 2 tablespoons of the olive oil until shimmering. Add the fennel, onions, garlic and a generous pinch each of salt and pepper. Cook over moderately low heat, stirring occasionally, until the vegetables are very tender, about 20 minutes. Add the raisins and oregano and cook for 30 seconds. Add the white balsamic vinegar and cook until evaporated, about 2 minutes. Stir in the mint and the reserved raisin soaking liquid and season the relish with salt and pepper.
In a large nonstick skillet, heat the remaining 2 tablespoons of olive oil until shimmering. Pat the fish dry and season with salt and pepper. Add the fillets to the skillet, skin side down, and cook over high heat for 30 seconds, pressing the fish flat with a spatula. Reduce the heat to moderate and cook until the skin is well browned, about 5 minutes.
Turn and cook until the fish is just white throughout, about 3 minutes longer. Transfer the fish to plates, skin side up, top with the relish and serve.
The cipollini, fennel and raisin relish can be refrigerated for up to 3 days. Bring to room temperature before serving.
Green raisins, also called kishmish, come from Iran, Afghanistan or Pakistan. They are available at some Middle Eastern groceries and khanapakana.com.