Combine the Marinara, cream, vodka and red pepper flakes in a medium saucepan. Bring to a boil over medium-high heat, then reduce the heat and simmer briskly until slightly thickened, about 10 minutes. Whisk in the Parmesan and take off the heat.
Meanwhile, cook the penne according to the package directions. Drain and add to the sauce, tossing to coat. Serve the pasta topped with basil leaves and additional Parmesan.
Classic Marinara Sauce:
Heat the olive oil in a large saucepan over medium heat. Add the garlic and cook, stirring frequently, until it just turns golden, 3 to 4 minutes. Add the tomatoes, Italian seasoning, basil, 1 teaspoon salt and a few grinds of fresh pepper. Bring to a simmer and cook, stirring occasionally, for 7 minutes. Take off the heat and stir in the butter until melted. Add salt and pepper to taste.