12 large cultivated white mushrooms, about 2 inches in diameter
3 tablespoons olive oil
3 tablespoons unsalted butter or olive oil
6 tablespoons finely minced onion
2 cloves garlic, finely minced
1/4 cup minced serrano ham (optional)
1/4 pound semicured chorizo, ground in a food processor
1/4 cup toasted or fresh bread crumbs
2 tablespoons chopped fresh flat-leaf parsley, thyme, or marjoram
Salt and freshly ground black pepper
1/4 cup grated Manchego cheese (optional)
Preheat the oven to 400°F. Carefully remove the stems from the mushrooms, and chop the stems finely. (You can do this in a processor, pulsing to chop.) You will need 1/2 to 2/3 cup chopped stems.
In a sauté pan, warm the oil over medium, high heat. Add the mushroom caps in batches and brown briefly on both sides, about 4 minutes total. Transfer to a cazuela or shallow baking dish, hollow side up, and set aside.
Wipe out the sauté pan and melt the butter over medium heat. Add the onion and cook, stirring, until softened, about 5 minutes. Add the garlic and the stems and cook, stirring, until the stems are wilted, about 3 minutes. Add the ham and chorizo and cook, stirring, until the chorizo is cooked, about 3 minutes. Stir in the bread crumbs and parsley, and season to taste with salt and pepper, keeping in mind that the ham will give off more salt in the heat of the oven.
Spoon the mixture into the mushroom caps, mounding it slightly. Sprinkle evenly with the cheese. (The mushrooms can be prepared up to this point 4 to 8 hours in advance, covered, and refrigerated. Bring to room temperature before baking.)
Bake until the cheese is melted and the mushrooms are hot and bubbling about 15 minutes. Serve from the cazuela or transfer to a platter and serve hot or warm.
Spanish: Hondarribi (Txacolina), rosé (Navarre, Cigales, Campo de Borja)
Non-Spanish: Alvarinho (Portugal), dry rosé (California)
Variations: Add 1/4 cup chopped toasted almonds to the stuffing with the parsley. Or, omit the cheese and add a pinch of ground cinnamon and 1 tablespoon grated orange zest with the chorizo.