Fill a large pot with salted water and bring to a boil. Cook 10 ounces penne until al dente according to package directions, then reserve a small cup of pasta water and drain the pasta.
While the pasta cooks, melt 2 tablespoons butter in a large skillet over medium-high heat.
Whisk in 1½ teaspoons flour and cook about 1 minute to remove the raw flour taste.
Add 3 cloves minced garlic and 1/3 cup chicken broth, whisking for about 1 minute until combined.
Pour in 1 cup heavy whipping cream and whisk for a few minutes until the sauce thickens enough to coat the back of a spoon.
Remove the skillet from heat, then stir in 1/2 teaspoon Italian seasoning, 1/2 teaspoon salt, 1/4 teaspoon pepper, and 1/2 cup freshly grated Parmesan until smooth.
Add the drained penne to the skillet and toss to coat; if needed, add a splash of reserved pasta water to loosen the sauce.