Preheat oven to 450 degrees
Spray a 12-inch pizza pan with non-stick cooking spray. Preheat oven to 450 degrees F.
In a large bowl toss potatoes with 1 tablespoon oil, oregano and garlic salt until evenly coated. Beginning along outer edge of pizza pan, arrange potato slices slightly over-lapping and in a circle, working toward center of pan forming a potato crust.
Bake potato crust at 450 degrees F for 23 to 25 minutes or until potatoes are tender and begin to brown.
Mix Fontina, Blue cheese and prosciutto together. In a non-stick skillet heat remaining 1 tablespoon oil to hot over medium-high heat. Add onion and cook 2 minutes, stirring often. Add tomatoes; cook 2 minutes or until softened, stirring often. Remove from heat. Stir in basil; set aside.
Once potato crust has baked, remove from oven and cover crust with cheese mixture. Spoon onion mixture evenly over cheese (there will be spaces) then top with olives. Return to oven to bake until cheese melts - about 8 minutes.
Remove from oven; let rest 3 minutes. Cut into wedges on pan.
Place a wide spatula and forks nearby for serving.
Note: Do not peel potatoes.
