2 tablespoons butter (1/4 stick), melted
1/4 cup chocolate-hazelnut spread (such as Nutella)
1/2 cup chopped bittersweet or semisweet chocolate
2 tablespoons chopped high-quality white chocolate (such as Lindt or Perugina)
2 tablespoons chopped toasted hazelnuts
Preheat oven to 450°F. Line large baking sheet with parchment. Roll out dough on lightly floured surface to 11-inch round. Transfer dough to prepared sheet. Make indentations all over dough with fingertips. Brush melted butter over. Bake until pale golden, about 20 minutes.
Smooth chocolate-hazelnut spread over hot crust. Sprinkle chopped bittersweet chocolate and white chocolate over. Bake until chocolate begins to melt, about 2 minutes. Sprinkle chopped hazelnuts over, cut into wedges, and serve.