How to Make It
Bring a large saucepan of water to a boil. Add the kale and cook until just tender, about 2 minutes. Drain, pressing out the excess water.
Using a 1 1/2-inch round cookie or biscuit cutter, punch out 32 rounds from the brioche slices (you can save the scraps to toast and grind for bread crumbs). In a large skillet, melt 2 tablespoons of the butter. Add half of the brioche rounds and toast over low heat, turning once, until golden, 3 minutes. Transfer the rounds to a work surface. Wipe out the skillet. Add 2 more tablespoons of butter and let it melt. Add the remaining brioche rounds and toast.
Wipe out the skillet and melt the remaining 2 tablespoons of butter in it. Add the shallots, garlic and thyme and cook over moderate heat, stirring, until softened, about 4 minutes. Add the mushrooms and cook until just tender, about 5 minutes. Add the kale and cook, stirring, for 2 minutes. Add the sherry and cook until evaporated. Add the cream, season with salt and pepper and cook until thickened, about 5 minutes. Stir in the parsley. Spoon the mixture onto the toasts and serve warm.