Make the condensed coconut milk
Give the coconut milk cans a shake before opening, pour into a large saucepan, and bring to a boil over medium heat. Boil, stirring occasionally, until reduced to 1-1/2 cups, 15 to 20 minutes. Set aside to cool completely. (The milk settles a bit as it cools. You will need 1 cup for the cupcakes and 1/3 cup for the frosting.)
Make the cupcakes
Position an oven rack in the center of the oven and heat the oven to 350°F. Line 18 regular-sized (2-3/4-inch diameter) muffin cups with paper or foil liners. Whisk the flour, baking powder, and salt in a medium bowl until well blended.
Put the butter in a large bowl. Beat with an electric mixer fitted with the paddle attachment on medium speed until well blended and smooth, about 1 minute. Add the granulated sugar and beat on medium-high speed until well blended, about 2 minutes. Add the eggs, one at a time, beating well after each addition. Add the vanilla with the last egg. Stop to scrape down the bowl and the beater as needed.
Add half of the flour mixture to the sugar mixture and mix on low speed until just blended. Add 1 cup of the cooled condensed coconut milk and mix just until blended. Add the remaining flour mixture and mix on low speed until just blended.
Portion the batter evenly among the prepared muffin cups (a scant 1/4 cup of batter per cup will be about two-thirds of the way full). Bake until a toothpick inserted in the center comes out clean, 18 to 20 minutes. Move to a wire rack and let cool for 15 minutes. Carefully remove the cupcakes from the pan and set them on a wire rack and let cool completely.
Make the frosting
While the cupcakes are cooling, make the frosting. Put the butter in a large bowl. Beat with an electric mixer fitted with the paddle attachment on medium speed until well blended and smooth, about 1 minute. Add the confectioners’ sugar, the remaining 1/3 cup of the cooled condensed coconut milk, the vanilla, and salt. Beat on medium-low speed until the sugar is combined. Scrape down the sides of the bowl and the beater. Increase the speed to medium high and beat until light and fluffy.
Assemble the cupcakes
Portion the frosting evenly among the cooled cupcakes (about 2 tablespoons per cupcake). Using a small metal spatula, mound and swirl the frosting on top of the cupcakes, leaving a border of cake around each one. Sprinkle each cupcake generously with the toasted coconut. Serve immediately; the cupcakes are best served at room temperature.
Make Ahead Tips
The coconut milk can be prepared and stowed in the refrigerator up to 5 days ahead. Bring to room temperature and stir before using.
The cupcakes can be prepared through Step 3, covered, and stowed at room temperature for up to 1 day before frosting.
The frosted cupcakes can be covered and refrigerated for up to 2 days. Bring to room temperature before serving.
Photo: Scott Phillips