Scallion Potato Cakes with Sausage Gravy

Name: Scallion Potato Cakes with Sausage Gravy
Ingredients: For the potato cakes; 4 medium potatoes, peeled and cut into 1 inch cubes (about 4 cups); 3 tablespoons butter; 1/2 cup half and half; 1/2 teaspoon salt; 1/4 teaspoon black pepper; 2 thinly sliced green onions (scallions); 1 egg, lightly beaten; 4 tablespoons all purpose flour; For the gravy and putting it all together; 3/4 pound bulk pork sausage; 2 tablespoons flour; 2 1/2 cups whole milk; 1 teaspoon black pepper; The previously made potato mixture; Sliced green onion for garnish; 1 tablespoon butter; 1 tablespoon peanut or vegetable oil