Preheat the oven to 400°F and adjust rack to the middle position.
Begin by preparing the meatballs. In a large bowl, mix together the ground beef, 1/2 cup of pecorino cheese, parsley, raw egg, garlic, 1/4 cup breadcrumbs, salt and black pepper until full combined. Once the mixed, roll into quarter sized meatballs and place on a baking sheet. Cook the meatballs for about ten minutes. Once they are ready, remove from the stove and set aside.
Meanwhile, spread the butter around all of the edges of a deep baking dish. I recommend using a deep cake pan with a removable bottom. Make sure the butter coats the whole inside of the pan to prevent sticking. To make a nice crust, add some breadcrumbs into the pan and then rotate it to allow the breadcrumbs to stick to the butter around the entire pan.
In a large mixing bowl, mix together the rice, tomato sauce, one cup of pecorino cheese, salt and black pepper.
Spread half of the rice mix evenly on the bottom of the breadcrumb lined pan. Sprinkle the pecorino cheese evenly over the layer of rice. Add a layer of mozzarella slices over the pecorino cheese. Sprinkle in the boiled eggs and then top it off with a layer of the meatballs. Cover with the remaining half of the rice mix. Flatten the rice mix to fully cover the top layer and pack all of the layers together.
Cook the sartu di riso in the oven for about forty minutes. Remove from the oven and set aside to cool off for about ten minutes to allow the layers to settle before cutting into it.
Remove the sartu di riso from the baking pan and enjoy a slice! Salute and cin cin!