Carefully remove lids from coconut milk cans without shaking them. Spoon about 1 cup of thick cream from tops of cans and place in a large, heavy pot with red curry paste.
Bring to a boil over high heat and cook, stirring frequently, until cream separates into colored oil and coconut solids, about 8-10 minutes.
Stir in remaining coconut milk, fish sauce, and brown sugar. Simmer for 5 minutes.
Add shrimp (and pineapple if using) and bring back to a simmer over moderate heat.
Cook until shrimp is almost done, 3-4 minutes, then add snow peas, bell pepper, and optional hot pepper.
Cook until vegetables are crisp-tender, about 2 minutes.
Remove from heat and stir in lime juice. Adjust seasoning with salt if necessary.
Garnish with whole basil leaves, mint leaves, and chopped peanuts. Serve with white rice.