Heat 4 teaspoons olive oil over medium-low heat in large skillet. Add yellow onion and cook until soft and golden brown, 20-30 minutes.
Meanwhile, poke the petite potatoes, a few times with the tip of a knife and microwave on high for 1 1/2 - 2 minutes or until softened. Cool potatoes, then cut into 1/4-inch slices.
Place 2 pizza pie crusts on a lightly oiled grill heated to medium. Cook for 2 minutes, or until bubbly and rigid. Using tongs, turn crusts over. Divide Fontina cheese, potato slices and sautéed onions over each crust.
Close lid, and cook until cheese is bubbly and crusts are golden brown, 2-3 minutes. Remove from grill and season with 2 tablespoons finely chopped Rosemary, and salt and pepper. Drizzle with 2 teaspoons olive oil,. Slice each pizza into 6 wedges. Enjoy!