Prepare a medium-hot fire in your grill, or heat a cast-iron grill pan over medium heat.
Roll the pizza dough into 8 small pizzas, each about 1/8-inch thick and 3 inches round.
Lightly brush both sides of the pizzas with oil. Grill the pizzas over medium heat until the first side is nicely browned and firm to the touch, 3 to 5 minutes. Turn the pizzas over on the grill. Spoon about 2 teaspoons of pesto on each pizza, spreading it to the edges. On top of each pizza, spoon 4 teaspoons of ricotta cheese, in little balls. Cook the pizzas until the ricotta just begins to melt, 3 to 5 minutes from the moment you turned the pizzas. Sprinkle Parmesan over the top of each pizza. Season with salt and freshly ground pepper. Serve warm.
Entertaining Notes: You don't need to make your own dough, not for a party of 8 people. Buy it from a local pizzeria. To work ahead, roll the dough into rounds about a half hour before your guests arrive and stack them, dusted with flour, at room temperature, between sheets of parchment paper.
Recipe courtesy Michael Chiarello