How to Make It
Preheat the oven to 450°. Coat a large roasting pan with 1/2 tablespoon of the olive oil. Add the onion, celery and garlic and stir to combine. Set the salmon on the vegetables, skinned side down, and rub with the remaining 1/2 tablespoon of olive oil. Season with the nutmeg and salt and pepper. Sprinkle the sage and rosemary all over the salmon and roast in the upper third of the oven for about 25 minutes, or until nicely glazed and just cooked through. Keep warm.
Spread 1/4 cup of the oil on a large rimmed baking sheet. Add the sweet potatoes, 3 of the garlic cloves, the shallots, thyme and nutmeg and toss well. Season with the cayenne pepper and salt and black pepper and roast in the lower third of the oven with the salmon, stirring a few times, for about 25 minutes, or until well browned.
Heat 1 tablespoon of the oil in a cast-iron skillet until almost smoking. Add the okra, season with salt and pepper and cook over high heat, stirring, until lightly charred, about 2 minutes. Transfer the okra to a bowl; keep warm.
Set the skillet to moderate heat. In a bowl, toss the shiitakes with the cayenne chile and the remaining 1 1/2 tablespoons of oil and season with salt and black pepper. Add the shiitakes to the skillet and cook, stirring, until tender, about 5 minutes. Add the remaining 2 garlic cloves and cook until the mushrooms begin to crisp, about 2 minutes. Stir the okra into the shiitakes and cook for 1 minute.
Cut the salmon into 6 pieces and place on 6 large plates. Spoon the vegetables around the fish and serve at once.