Cook the penne in a pot of salted boiling water according to package directions until al dente, then drain and set aside in a large bowl.
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.
Add the flour to the butter and garlic and stir until fully blended to form a paste (roux).
Gradually whisk in the chicken broth and evaporated milk, bring to a boil, then reduce heat and cook, stirring, for about 2 minutes until the sauce thickens.
Stir the cooked shrimp, shredded Parmesan, minced parsley, and seafood seasoning into the sauce and heat just until warmed through.
Pour the shrimp sauce over the drained penne in the large bowl and toss gently to coat. Serve immediately.