2 tablespoons extra-virgin olive oil, plus more for brushing
3/4 pound mixed mushrooms, such as button and cremini, sliced 1/4 inch thick
Salt and freshly ground pepper
1/2 small onion, thinly sliced
1/4 cup dry sherry, such as Oloroso
Four 1/2-inch-thick slices of rustic white bread
2 tablespoons unsalted butter
4 large eggs
2 tablespoons coarsely chopped flat-leaf parsley
Preheat the oven to 400°. In a large skillet, heat the 2 tablespoons of oil until shimmering. Add the mushrooms and season with salt and pepper. Cover and cook over moderate heat, stirring a few times, until softened, 4 minutes. Add the onion, cover and cook, stirring occasionally, until the onion is softened and the mushrooms are browned, 3 minutes longer. Add the sherry and cook until almost evaporated, 1 minute. Season with salt and pepper. Remove from the heat, cover and set aside.
Arrange the bread slices on a large rimmed baking sheet and brush with olive oil. Bake for about 6 minutes, until toasted. Transfer the toasts to plates.
In a large, nonstick skillet, melt the butter over moderate heat. Crack the eggs one at a time into a ramekin and then slip into the skillet. Cook the eggs, sunny-side up, until the whites are firm and the yolks runny, about 5 minutes.
Spoon the mushroom mixture onto the toasts and top with the fried eggs. Garnish with the parsley and serve.
The cooked mushrooms can be refrigerated overnight. Reheat gently.
This dish could go well with either an earthy red, such as a Pinot Noir, or a crisp white, like a Pinot Gris.