1. Dissolve yeast and sugar in the warm water in a small bowl; let stand 2 minutes. Pulse flour and salt in a food processor twice to combine. Add yeast mixture and pulse just until moistened. With machine running, pour oil through feed tube and process just until dough begins to leave sides of bowl and forms a ball. On a lightly floured surface, knead dough 1 minute, until smooth and elastic. Form into a ball and place in oiled bowl, turning to oil top. Cover with a clean kitchen towel and let rise in a warm draft-free place 15 to 20 minutes, until doubled in bulk.
2. Heat oven to 425 degree F. Lightly oil a 10-inch cast-iron skillet. Press dough along bottom and up sides of skillet to a make raised edge. Bake 8 to 10 minutes or until lightly browned.
3. Meanwhile, remove sausage from casings and cook in a small saucepan over medium heat 5 to 7 minutes or until completely cooked; drain. Remove crust from oven and prick any air bubbles with a fork. Pour pizza sauce evenly over crust. Sprinkle sausage, then cheeses on top. Bake pizza in skillet 10 minutes more or until cheese is melted. Sprinkle with chopped parsley. Makes 4 servings.