PREHEAT oven to 425°F.
COMBINE 1 cup flour, undissolved yeast, sugar and salt in a large bowl. Add very warm water and oil; mix until well blended, about 1 minute.
Gradually add enough remaining flour to make a soft dough. Dough should form a ball and will be slightly sticky. Knead** on a floured surface, adding additional flour if necessary, until smooth and elastic, about 4 minutes.
PAT dough with floured hands to fill greased pizza pan or baking sheet. OR roll dough on a floured counter to 12-inch circle; place in greased pizza pan or baking sheet.
PULL or cut each stick of string cheese into 2 pieces lengthwise. Lay each piece around the outer edge of the pizza dough. Bringing edge of dough over cheese, pressing to encase the cheese in the dough.
SPREAD with pizza sauce. Top with mushrooms and sausage and sprinkle with cheese. BAKE on lowest oven rack for 15 to 18 minutes, until cheese is bubbly and crust is browned.