Preheat the oven to 325ºF. Prepare the cupcake pan by lining with cupcake liners.

In a stand mixer using the paddle attachment, combine the unsalted butter, coconut oil, granulated sugar, baking powder, baking soda, and kosher salt.

Start by mixing on low to moisten before increasing to medium speed and cream together until the mixture is light and fluffy. This will take about 5 minutes. Be sure to scrape down the sides and bottom of the mixing bowl halfway through to prevent any lumps from forming.

While still mixing on low speed, gradually add the egg whites, mixing well after each addition, before following with the vanilla bean paste.

Add 1/3 of the cake flour, followed by 1/3 of the buttermilk, alternating additions until everything is incorporated.

Pour the cupcake batter into the prepared cupcake pan. Bake for 20-22 minutes, or until a toothpick inserted comes out clean.

In a stand mixer, using the paddle attachment, beat the softened unsalted butter for 3 minutes on high speed, or until the butter is creamy and slightly pale.

Add the vanilla bean paste, kosher salt and half of the powdered sugar. Mix together until everything is mostly combined

Add the remaining powdered sugar and mix on high speed for 1-3 minutes, or until it is fully combined and smooth. Scrape down the bottom and sides of the mixing bowl to prevent any lumps from forming.

Add the heavy cream and mix until the buttercream is smooth.

Adjustments: If the buttercream is too sweet you can add a pinch of kosher salt to reduce the sweetness. If the buttercream is too thin, you can add more powdered sugar, 1/4 cup at a time. If the buttercream is too thick, you can add heavy cream, one tablespoon at a time.

Frost your cupcakes and enjoy!