Pulse 1 1/2 cups of flour with salt and optional sugar in a food processor. Add cold butter and process until it looks like a paste. Add remaining flour and pulse until crumbly. Move to a bowl, add 4 tbsp of ice water, mixing until the dough holds together. Shape into a ball, cut in half, flatten each half, wrap, and chill for at least 1 hour.

Roll one disk on a floured surface, fit it into a 9-inch pie dish. Crimp the edge and prick the bottom with a fork. Chill the shell for 30 minutes. Preheat oven to 400°F. Line crust with parchment and pie weights, bake for 20 mins. Remove weights, bake for another 10 mins. Let cool completely.

Dissolve cornstarch in 1 cup water. In a saucepan, heat coconut milk, whole milk, and sugar. Stir in cornstarch mixture, keep stirring until thick. Divide into two bowls.

Melt chocolate chips and stir into one bowl of haupia until smooth. Beat heavy cream with 1/4 cup sugar until stiff peaks form.

Spread chocolate haupia over cooled crust, then add the plain haupia. Top with whipped cream. Chill for at least 1 hour before serving.

Cover and store in the refrigerator for about 3 days. For longer storage, wrap tightly and freeze for up to 1 month. Thaw overnight in the fridge before serving.