Step 1: Prepare the Tart Crust

1. In a food processor, combine flour, sugar, and salt. Add cold butter and pulse until the mixture resembles coarse crumbs.
2. Add the egg yolk and 2 tbsp cold water, pulsing until the dough starts to come together. If needed, add an extra tbsp of water.
3. Shape the dough into a disk, wrap in plastic wrap, and refrigerate for at least 30 minutes.
4. Preheat oven to 350°F (175°C). Roll out the dough and cut into small circles to fit a muffin tin or mini tart molds.
5. Press the dough into the molds, poke holes in the bottom, and bake for 12-15 minutes, or until golden brown. Let cool.

Step 2: Make the Coconut Cream Filling

6. In a medium saucepan over medium heat, whisk together whole milk, coconut milk, sugar, cornstarch, and salt.
7. In a separate bowl, whisk the egg yolks. Slowly add a small amount of the warm milk mixture to the yolks, stirring constantly to temper them.
8. Pour the egg mixture back into the saucepan and cook until thickened (about 3-5 minutes), stirring constantly.
9. Remove from heat, then stir in vanilla extract, shredded coconut, and butter.
10. Allow the filling to cool slightly before spooning into the cooled tart shells. Refrigerate for at least 1 hour to set.

Step 3: Add the Topping

11. Whip the heavy cream, powdered sugar, and vanilla extract until stiff peaks form.
12. Pipe or spread the whipped cream over the chilled tarts.
13. Garnish with toasted coconut flakes.