Make-ahead: cook the chowder through the potato simmer and refrigerate it without the shrimp, corn, cream or butter. Sear the shrimp fresh the next day and finish the pot in five minutes.
Storage: leftovers keep 3 days in the fridge. Reheat gently over low heat and stop as soon as the surface steams, because a hard boil breaks the dairy and toughens the shrimp.
Freezing: freeze the base only, before the dairy goes in, for up to 3 months.
Doneness: a cooked shrimp is opaque and curled into a loose letter C. A tight O means it has gone too far.
Substitutions: full-fat coconut milk for the milk and cream, or bay scallops for half the shrimp. Nutrition values are an estimate.