Set the pasta machine to its widest setting. Flatten the dough into a rectangle 3 inches wide. Run the rectangle through the machine 4 to 5 times to begin stretching dough. Run the dough through the machine, adjusting to the next narrower setting after every 2 passes. Cut crosswise into 3 equal pieces. Run each piece through the machine at the lowest setting. Using a sharp knife, cut each piece into wide strips. Dust the pappardelle with semolina and set aside.
For the sausage and sauce: In a cast iron skillet, add the sausage and begin to brown on all sides, 6 minutes. Heat the oil in a 6-quart saucepan over medium-high heat. Add the garlic and onions, and saute until translucent. Add the sausage and sherry, and stir to combine. Add the tomatoes and dried oregano and parsley. Bring to a boil, then simmer for 1 hour. Stir in the cheese and parsley.
In a large pot of boiling salted water, add the pappardelle and cook until the pasta floats to the top, about 2 minutes. Drain the pasta. Place a ladle full of sauce down on each plate and top with the pasta and some sausage. Ladle more sauce on top and garnish with a parsley sprig.