Peel and devein the shrimp. Rinse the heads and the shells and put them into a saucepan with just enough water to cover, along with the bulb ends of the green onions and the peppercorns. Bring the saucepan to a bare simmer and hold there for about a half-hour. Strain and reserve the stock.
Heat the olive oil over medium heat in a large skillet. When hot, add the peeled shrimp and cook while agitating the pan (so the shrimp will turn over) until the shrimp are pink. Remove the shrimp from the pan.
Add the garlic, crushed red pepper, parsley, green onions, and mushrooms to the skillet. Cook about another minute.
Add the wine and one cup of the shrimp stock. Bring to a boil. Reduce to a light sauce consistency, then remove from the heat. Whisk in the softened butter, and add the salt.
Return the shrimp to the pan and cook about two minutes more, until firm. Adjust salt and pepper to taste.
Add the pasta to the pan and toss it around with the sauce and shrimp. Serve garnished with fresh oregano and fresh chopped parsley.
