Preheat oven to 350°. Line 18 muffin cups with paper liners.
Cream butter and sugar until light and fluffy. Beat in vanilla and 1 egg white at a time, beating well after each addition. In another bowl, whisk together flour, baking powder, baking soda and salt; add to creamed mixture alternately with buttermilk, beating after each addition.
Fill prepared cups about two-thirds full. Bake until a toothpick inserted in center comes out clean, 17-20 minutes. Cool 10 minutes. Remove cupcakes to a 15x10x1-in. pan.
In a bowl, mix sweetened condensed, evaporated and coconut milks. Poke holes in cupcakes with a skewer, about 1/2 in. apart. Slowly spoon milk mixture over top, allowing it to absorb into cake. Refrigerate, covered, at least 2 hours.
To serve, beat cream until it begins to thicken. Add confectioners' sugar; beat until soft peaks form. Spread or pipe over cupcakes. Top with coconut. Store in the refrigerator.