In a large, heavy skillet, heat the oil over low heat. Add the onions, salt, pepper, herbs de Provence, and sugar. Stir to combine. Continue cooking over very low heat, stirring occasionally, until the onions are caramelized and dark golden brown, about 1 hour and 45 minutes.
Preheat the oven to 475 degrees F.
Roll out the pizza dough into a 1/4-inch-thick round. Using the cookie cutter, cut out 24 dough circles. Arrange the circles on a large heavy baking sheet.
Place a small spoonful of the caramelized onions on each dough circle. Top with a small amount of goat cheese.
Bake until golden and bubbly, about 10 minutes.
While still hot, top each pizzette with a piece of prosciutto. Arrange on a serving platter and garnish with sprigs of parsley or rosemary. Serve immediately.