To prepare a stuffed portobello mushroom with egg and pesto recipe, first you need to prepare the mushrooms. First, you'll need: 1 pound (240 g) of mushrooms, 2 tablespoons (60 ml) olive oil, 1 teaspoon (2.5 tsp) kosher salt, and 1 tablespoon (1.25 cm) freshly ground black pepper. You can use any type of mushroom you like, as long as it isn't too big or too small. Then, cut the mushroom in half lengthwise and scoop out the insides. Fill each half with the stuffing of your choice, such as prosciutto, ricotta, or feta cheese. Bake in the oven at 400 ?F (204 C) for 20 to 25 minutes or until the cheese is melted and the filling is heated through. Serve with sour cream and parsley.