Keep an eye on shrimp; they become rubbery if overcooked. Remove as soon as they turn pink and opaque., Reserve some pasta water; its starch helps achieve a silky smooth sauce., Use freshly grated Parmesan for better melting and flavor versus pre-shredded cheese., Add cheese slowly over low heat and stir constantly to prevent grainy or separating sauce., If sauce breaks or curdles, whisk in warm pasta water or more cream off heat to restore texture., Add a squeeze of lemon juice or zest at the end for brightness., Substitutions include using fusilli or rigatoni instead of penne, cooked shredded chicken or scallops in place of shrimp, adding cherry or sun-dried tomatoes, toasted pine nuts for crunch, or deglazing skillet with white wine before cream for depth., To lighten sauce, use half-and-half plus cornstarch slurry instead of heavy cream., Store leftovers in an airtight container in the fridge up to 3 days; reheat gently with splash of milk, cream, or broth to loosen sauce., Freeze pasta and sauce separately from shrimp for up to one month; thaw overnight and reheat gently., To prep ahead, cook pasta and sauce separately from shrimp and combine before serving.