How to Make It
Preheat the oven to 425º. In a large saucepan, melt 2 tablespoons of the butter in 1 tablespoon of the olive oil. Add the spinach in large handfuls, letting each batch wilt slightly before adding more. Cook the spinach over high heat, stirring occasionally, until wilted, about 7 minutes. Transfer the spinach to a strainer set over a large bowl to drain. Let the cooked spinach cool slightly, then squeeze out all of the excess water from the leaves.
Wipe out the saucepan, then use it to melt the remaining 2 tablespoons of butter in the remaining 1 tablespoon of olive oil. Add the shallots and cook over moderately high heat, stirring, until softened, about 3 minutes. Add the white wine and cook, stirring, until absorbed, about 3 minutes. Add the heavy cream and bring just to a boil. Simmer over moderate heat, stirring occasionally, until reduced by half, about 7 minutes. Stir in the Salted Herbs and season lightly with pepper.
Fold the spinach into the cream sauce and scrape the mixture into a buttered 1 1/2-quart baking dish. Bake the creamed spinach for about 15 minutes, until bubbling and the sauce is thickened. Let stand for 5 minutes before serving.