Preheat the oven to 400°F. Place rack in middle position.
Meanwhile, in a medium mixing bowl, scramble the eggs, salt, black pepper and milk.
Once scrambled, add in the pecorino cheese and whisk until fully mixed in. Set aside.
In an oven safe sauté pan, warm up a drizzle of olive oil over medium to high heat. Add in the sausage and sauté until browned.
Once the sausage is browned, add in the wild onions (lampascioni). Sauté the sausage and wild onions for about two minutes.
Pour the egg mixture into the sauté pan. Mix together to evenly distribute into the pan and lower the heat to low. Continue to cook until the outer rim of the frittata is firm/partially cooked.
Once the outer rim has firmed up, sprinkle the mozzarella cheese over the whole frittata. Place into the oven and cook for fifteen to twenty minutes.
Remove from the oven and let cool off for five to ten minutes before removing from the pan.