Prepare your wooden burning brick oven according to manufacturer's directions or preheat a conventional oven to 400 degrees F.
To make the stuffing, put the raisins, olives, pine nuts, parsley, and garlic on a cutting board and chop everything up; put into a mixing bowl. Add the sausage and 1/2 cup of the cheese. Drizzle the stuffing with about 1/4 cup of olive oil to moisten and season with salt, pepper, and red pepper flakes; mix well with your hands to combine. Put the bread crumbs in another bowl, drizzle with a bit of olive oil and add 1/4 cup of the pecorino; season with salt and pepper.
Oil the bottom and sides of an earthenware or casserole dish, which is large enough to hold all the mushrooms in a single layer. Arrange the mushrooms snugly in the pan, cap-side down; season the insides with salt and pepper and drizzle with olive oil. Stuff each mushroom with a generous spoonful of the sausage stuffing and sprinkle the bread crumbs on top; drizzle with even more oil. Bake for 20 minutes until the stuffing is browned and the mushrooms soft, rotating the dish periodically for even cooking.