Bring a large pot of salted water to a boil, then add the penne and cook until just shy of al dente, about 10-12 minutes. Drain and set aside, reserving about ½ cup of pasta water.
While the pasta cooks, melt the butter in a large skillet over medium heat and add the minced garlic. Sauté for about 30 seconds until fragrant, listening for a gentle sizzling and watching the garlic turn slightly golden.
Add the cooked shrimp to the skillet, stirring gently to warm through or cook until heated if raw, about 2-3 minutes. Remove the shrimp from the skillet and set aside.
Pour the heavy cream into the skillet with the garlic butter, bringing it to a gentle simmer. Cook for about 2 minutes, stirring constantly, until the sauce starts to thicken slightly and turns a rich, creamy color.
Gradually stir in the grated Parmesan cheese, a handful at a time, until melted and smooth. If the sauce becomes too thick, loosen it with a splash of the reserved pasta water.
Return the shrimp to the skillet, tossing gently to coat them in the sauce. Add a squeeze of lemon juice and season with salt and pepper to taste. Let everything cook together for another 1-2 minutes.
Add the cooked penne to the skillet and toss well to coat the pasta evenly with the creamy sauce. If needed, add a little more reserved pasta water to reach your desired consistency.
Sprinkle with chopped parsley for a fresh, vibrant touch. Remove from heat and let sit for a minute to allow the sauce to cling beautifully to every strand of pasta.
Serve immediately, garnished with extra Parmesan and lemon wedges if desired. Enjoy your comforting, cheesy shrimp Alfredo penne!
