Ingredients

1. 3 tablespoons extra-virgin olive oil
2. 1/3 cup finely chopped onion
3. 1 garlic clove, minced
4. 1 medium tomato--peeled, seeded and coarsely chopped
5. 1/2 pound lean ground pork
6. 3 tablespoons chicken stock or canned low-sodium broth
7. 1 tablespoon tomato paste
8. 1/2 teaspoon fennel seeds, coarsely chopped
9. Salt and freshly ground pepper
10. 10 white mushrooms with 2-inch-wide caps, stems discarded

Directions

1. Heat 1 tablespoon of the oil in a large skillet. Add the onion and cook over moderately low heat, stirring, until softened, about 10 minutes. Add the garlic and cook until fragrant, about 1 minute. Add the tomato and cook, stirring occasionally, until the liquid is evaporated and the sauce is thick, 7 to 8 minutes.
2. Transfer the sauce to a bowl and wipe out the skillet. Add 1/2 tablespoon of the oil and heat until shimmering. Add the pork in small clumps and cook over moderately high heat until browned, 8 to 10 minutes. Add the tomato sauce along with the chicken stock, tomato paste and fennel seeds and cook over low heat until thickened, about 5 minutes. Season the picadillo with salt and pepper and transfer to a plate.
3. Preheat the oven to 350°. Using a melon baller or small spoon, scrape out the brown gills from the mushroom caps. Wipe out the skillet again and heat the remaining 1 1/2 tablespoons of olive oil until shimmering. Add the mushrooms, top side down, and cook over moderately high heat until golden brown, about 2 minutes. Turn the mushrooms and cook until brown on the other side, about 2 minutes longer.
4. Transfer the mushroom caps to a medium baking dish and fill them with the picadillo. Bake the mushrooms for about 15 minutes, or until cooked through. Transfer the mushrooms to a platter or individual plates and serve.

Make Ahead

The picadillo can be refrigerated for up to 2 days. Let return to room temperature before filling and baking the mushrooms.