Bring a large pot of salted water to a boil and cook 10 ounces penne until al dente according to package directions, then reserve a little pasta water and drain.
While the pasta cooks, melt 2 tablespoons butter in a large skillet over medium-high heat.
Whisk in 1 1/2 teaspoons flour and cook about 1 minute to remove the raw flour taste.
Add 3 minced garlic cloves and 1/3 cup chicken broth, whisking for about 1 minute until combined.
Pour in 1 cup heavy whipping cream and whisk continuously until the sauce thickens enough to coat the back of a spoon, about 2–3 minutes.
Remove the skillet from heat and stir in 1/2 teaspoon Italian seasoning, 1/2 teaspoon salt, 1/4 teaspoon pepper, and 1/2 cup freshly grated Parmesan until melted and smooth.
Add the drained penne to the sauce and toss to coat, adding a splash of reserved pasta water if needed to loosen the sauce.
