- 4 russet potatoes
- 3 tablespoon extra-virgin olive oil
- 1 small onion, chopped
- 8 ounces small mushrooms, such as cremini or button, sliced
- 3 cloves garlic, minced
- 1/4 teaspoon salt, plus more for seasoning
- 1/4 teaspoon freshly ground black pepper, plus more for seasoning
- 1 1/2 sticks of butter
- 1 1/2 teaspoons dried oregano
- 1 1/2 cups shredded cheddar
- 1/3 cup chopped fresh flat-leaf parsley
Using the tines of a fork, prick the skins of the potatoes all over and arrange on the prepared baking sheet. Bake for 1 to 1 1/4 hours until tender and cooked through. Remove from the oven and let cool until warm enough to handle, about 20 minutes.
Arrange the potato halves, cut side up on the baking sheet. Using a pastry brush, brush both sides of the potatoes with 2 tablespoons of melted butter and season the inside with salt and pepper, to taste. Spoon the mushrooms mixture into each potato half. Arrange 1 half-piece of prosciutto on top and sprinkle with the remaining cheese. Bake until the cheese is melted about 20 to 25 minutes. Remove from the oven, transfer to a serving platter, garnish with chopped parsley and serve.