Preheat oven to 400°F (205°C). Line two baking sheets with parchment paper or silicone mats. In a medium saucepan, bring water, butter, and salt to a rolling boil over medium-high heat.

Remove from heat and immediately add all the flour at once. Stir vigorously with a wooden spoon until the mixture forms a smooth ball and pulls away from the sides of the pan, about 1 minute.

Return the pot to medium-low heat and cook, stirring constantly, for 2 minutes to dry out the dough. A thin film should form on the bottom of the pan. Transfer dough to a large bowl and let cool for 5 minutes.

Beat in eggs one at a time with a wooden spoon or hand mixer, mixing thoroughly after each addition until completely incorporated and the dough is smooth and glossy. The dough should form a thick ribbon when lifted with a spoon.

Transfer dough to a piping bag fitted with a 1/2-inch round tip. Pipe 2-inch mounds onto prepared baking sheets, spacing them 3 inches apart. Use a wet finger to gently smooth any peaks.

Bake for 25 minutes without opening the oven door, then reduce temperature to 350°F (175°C) and bake for another 15-18 minutes until deep golden brown and shells feel light and hollow. Turn off oven, crack the door open, and let shells cool inside for 10 minutes.

While shells bake, make the filling: Open the chilled coconut milk and scoop out only the thick white cream from the top, leaving the watery liquid behind. You should have about 1 cup of thick cream.

Beat the coconut cream, powdered sugar, and vanilla extract with a hand mixer on medium-high speed for 3-4 minutes until thick, fluffy, and stiff peaks form. Refrigerate until ready to use.

Once shells are completely cool, cut each in half horizontally or cut a small slit in the side. Pipe or spoon coconut cream into the bottom half, then replace the top. Dust generously with powdered sugar just before serving.