Heat the oven to 350°F. Grease two baking sheets liberally with coconut oil, and set aside.

Add Guinness and butter to a saucepot, and bring to a simmer over medium heat. Add cocoa powder, and whisk until combined and no lumps remain. Transfer mixture to the freezer, and cool for 10 minutes.

Meanwhile, in a large mixing bowl, whisk flour, sugar, baking soda, and salt. Set aside.

In a stand mixer using the paddle attachment, beat eggs and yogurt on medium speed until combined. Remove the Guinness mixture from the freezer, and add to the egg mixture. Beat on low speed until just combined. Add flour mixture, and beat on low speed for 10 seconds. Using a rubber spatula, fold batter by hand until completely combined.

Pile 3 tablespoons of batter on the baking sheet, spacing each a few inches apart. Bake for 12 minutes, or until a toothpick inserted into each cake comes out clean. Cool for 10 minutes on the baking sheet, then transfer to a wire rack to cool completely. Repeat until no batter remains.

Using a stand mixer fitted with the paddle attachment, cream together the goat cheese and butter for 1 minute, or until smooth. Add vanilla and salt, and mix until combined. Reduce speed to medium-low, and slowly add confectioner’s sugar. Once sugar is slightly incorporated, increase speed to medium-high, and beat until combined.

Once cooled, turn over half the cakes so the flat side is face up. Place 2 heaping tablespoons of filling on each face-up cake, and top with another cake (flat side face down). Press gently to “glue” the cakes together with the filling. Wrap each whoopie pie in plastic wrap, and chill at least 1 hour, and up to overnight. Serve cool.