Bring a large pot of salted water to a boil. Add the penne pasta and cook according to the package instructions until al dente, about 10-12 minutes.
While the pasta cooks, melt the unsalted butter in a large skillet over medium heat.
Add the minced garlic to the skillet and sauté for 1-2 minutes until fragrant, stirring frequently to avoid burning.
Pour in the heavy cream and bring to a gentle simmer. Cook for 3-4 minutes, stirring occasionally, until the cream slightly thickens.
Stir in the basil pesto and grated Parmesan cheese until the sauce is smooth and creamy. Season with salt and black pepper.
Drain the cooked pasta, reserving 1/4 cup of the pasta water.
Add the drained pasta to the skillet with the creamy pesto sauce. Toss to coat the pasta evenly, adding reserved pasta water a little at a time if the sauce is too thick.
Remove from heat and stir in the chopped fresh basil leaves.
Serve immediately, garnished with additional Parmesan cheese if desired.