To make scooping the cream from a can of coconut milk easier, refrigerate the can for 24 hours and do not shake it.
Carefully spoon off about 1 cup of top layer of cream from 1 can of coconut milk. Whisk coconut cream and curry paste together in Dutch oven. Bring to simmer over high heat and cook until almost all of liquid has evaporated, 5 to 7 minutes. Reduce heat to medium-high and continue to cook, whisking constantly, until oil separates from solids and mixture is darkened and aromatic, 4 to 8 minutes.
Whisk in remaining coconut milk, fish sauce, and sugar. Bring to simmer and cook until flavors meld and sauce is thickened, about 5 minutes. Stir in shrimp and mushrooms and cook for 5 minutes. Stir in snow peas, bell pepper, and Thai chile, if using, and cook until vegetables are crisp-tender and shrimp are opaque throughout, about 2 minutes. Off heat, stir in basil, mint, and lime juice. Season with salt to taste. Serve.
