Bring a large pot of salted water to a boil and cook the penne according to package directions until al dente; drain in a colander and set aside.
While the pasta cooks, melt the butter in a large saucepan over medium heat and sauté the minced garlic until fragrant, about 30–60 seconds.
Whisk in the flour until blended and cook 1 minute, then gradually whisk in the chicken broth and evaporated milk until smooth.
Bring the sauce to a boil, reduce heat and simmer, stirring, for about 2 minutes or until slightly thickened.
Stir the cooked shrimp, Parmesan cheese, minced parsley, and seafood seasoning into the sauce and heat through, about 1–2 minutes.
Transfer the drained penne to a large bowl, pour the shrimp sauce over the pasta, and toss until evenly coated; serve immediately.