Layer store-bought pizza dough with potatoes, prosciutto, and scallions for one quick, addicting flatbread.
Preheat oven to 500°. Coat rimmed baking sheet with oil. Stretch dough to fit baking sheet. Thinly spread Dijon on dough. Top with potato, cheese, and scallion whites; season. Bake until dough is browned in spots and cheese is bubbly, about 15 minutes. Top with prosciutto and scallion greens.