Bring a large pot of salted water to a boil. Add the penne pasta and cook it according to the package instructions until al dente. Drain the pasta and set it aside.
In a large skillet, heat the olive oil over medium heat. Add the finely chopped onion and cook for about 2-3 minutes, or until it becomes translucent. Stir in the minced garlic and cook for an additional 30 seconds to 1 minute, until fragrant.
Pour in the vodka and stir well. Allow it to simmer for about 3-4 minutes, or until the vodka reduces by half.
Stir in the crushed tomatoes, and bring the mixture to a gentle simmer. Allow it to cook for about 10-15 minutes, stirring occasionally, until the sauce thickens slightly.
Reduce the heat to low and pour in the heavy cream, stirring to combine. Simmer for an additional 5 minutes, allowing the sauce to thicken and meld flavors.
Stir in the grated Parmesan cheese until it's fully melted and the sauce is creamy. Season with salt, freshly ground black pepper, and crushed red pepper flakes if you like a bit of heat. Adjust the seasonings to taste.
Add the cooked penne pasta to the sauce in the skillet. Toss the pasta in the creamy vodka sauce until it's well coated.
Plate the Penne alla Vodka, garnish with fresh basil leaves if desired, and serve immediately. Optionally, sprinkle some extra grated Parmesan on top before serving.