How to Make It
In a very large skillet, heat 1 tablespoon of the olive oil. Add the shrimp, season with salt and pepper and cook over moderate heat, turning a few times, until pink and curled, about 3 minutes. Transfer the shrimp to a large plate.
Add 1 tablespoon of the olive oil to the skillet and, when it's hot, add the sliced mushrooms. Cook over moderately high heat, stirring a few times, until any liquid evaporates and the mushrooms are browned, about 7 minutes. Push the mushrooms to the side of the skillet and add 1 more tablespoon of the olive oil. Add the sliced garlic and cook over low heat until golden, about 1 minute. Toss the garlic together with the mushrooms in the skillet and season with salt and pepper. Transfer the mushrooms and garlic to the plate with the shrimp.
Add the remaining 1 tablespoon of olive oil to the skillet. Season the halibut steaks with salt and pepper and add them to the skillet. Cook over moderate heat for about 3 minutes, then carefully turn the halibut. Add the Albariño, cover and cook until the halibut is just white throughout, about 2 minutes longer.
Return the shrimp and mushrooms to the skillet along with any accumulated juices and stir gently until heated through. Remove the skillet from the heat and season the pan sauce with salt and pepper. Transfer the halibut steaks to plates. Spoon the shrimp, mushrooms, and Albariño sauce over the fish and serve immediately with crusty bread.