Preheat your oven to 350°F. Line a 12-cup muffin pan with paper liners and set aside.

In a medium bowl, whisk together the cake flour, baking powder, and salt until well combined and light.

In a large bowl, use a hand mixer or stand mixer with the paddle attachment to beat the butter, oil, and sugar on medium speed until creamy and well blended.

Add the eggs one at a time, beating well after each addition and scraping down the sides of the bowl as needed.

Add one-third of the flour mixture to the butter mixture and stir with a spatula until just combined. Then add half of the coconut milk, the passionfruit pulp, and the vanilla, stirring gently. Repeat with another third of the flour, the remaining coconut milk, and finally the last of the flour, mixing only until just combined.

Divide the batter evenly among the prepared muffin cups, filling each about two-thirds to three-quarters full.

Bake for 18 to 20 minutes, until a toothpick inserted into the center comes out with just a few moist crumbs. Let the cupcakes cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.

In a small saucepan, whisk together the coconut milk, flour, and half of the sugar until smooth. Cook over low heat, stirring constantly, for 5 to 6 minutes until the mixture thickens into a very thick paste that holds lines from the whisk and no longer smells of raw flour.

Pour the paste into a bowl, press plastic wrap directly onto the surface to prevent a skin from forming, and refrigerate until completely cold.

In a large bowl, beat the butter and the remaining sugar on medium-high speed until very light and creamy, about 5 minutes, scraping down the sides occasionally.

Add the cooled milk paste and a pinch of salt. Beat on medium-high speed for 5 to 7 minutes. The mixture may look separated at first, but keep beating until it becomes smooth and fluffy, like whipped cream.

Once the cupcakes are completely cool, use a small knife or a cupcake corer to remove a 3/4-inch wide core from the center of each cupcake. Fill each hole with a generous teaspoon of passionfruit curd.

Pipe a ring of coconut buttercream around the top edge of each cupcake, then pipe a small dollop in the center to cover the curd, leaving a slight indentation. Add a little more passionfruit curd into the indentation.

If desired, sprinkle shredded coconut over the frosting and add a small drizzle of passionfruit pulp for extra flavor and decoration.