Mix flour, salt, sugar, and cold butter until crumbly. Add ice water until dough forms. Divide into 12 balls, press into muffin tins, and chill 30 minutes.
Bake at 375°F for 12–15 minutes. Cool completely. Shortcut: Use pre-made tart shells or phyllo cups.
Whisk coconut milk, whole milk, sugar, salt, and cornstarch in a saucepan. Cook over medium heat, stirring until thick, 5–7 minutes.
Temper egg yolks with ½ cup hot mix, return to pot, and cook 2–3 minutes more. Stir in vanilla, shredded coconut, and optional butter.
Fill crusts with warm custard. Cover with plastic wrap touching the surface. Chill at least 2 hours or overnight.
Beat cold cream, powdered sugar, and vanilla until soft peaks form. Add mascarpone or cream cheese if desired. Don’t overwhip.
Top with whipped cream, toasted coconut, and optional lime zest or white chocolate curls.