Preheat oven to 350℉. Line two cupcake tins with liners.
In a medium bowl, whisk together the 2 cups oat flour , ¼ cup almond flour2 ½ teaspoons baking soda, and ¼ teaspoon fine sea salt. Pour the 1 cup Guinness or gluten-free stout into a large saucepan, slice up the ½ cup unsalted butter, and add it to the beer. Heat over medium heat until the butter melts. Whisk in the ¾ cup unsweetened cocoa powder and 2 cups sugar, then set aside to cool briefly.
In a large bowl, whisk the 2 large eggs with the ⅔ cup plain Greek yogurt and 1 tablespoon pure vanilla extract Pour in the beer mixture, then stir in the flour mixture.
Divide the batter equally between the cupcake tins (I got about 24 cupcakes), place in the oven, and bake until risen and firm, about 25 minutes, and a tester inserted in a cupcake comes out clean. Remove from oven and let cool 5 minutes in the pan, then turn out onto a rack to cool completely.
Make Frosting
In a large bowl, whip the 8 oz. cream cheese with an electric mixer. Sift in the 1 cup powdered sugar and beat to incorporate, then . beat in the ¼ cup heavy cream.
Frost each cooled cupcake.
Notes
Hydrate the batter. Make sure to let the batter rest while the oven heats. Gluten-free flours benefit from a rest before baking so that the batter can hydrate.
Bring frosting ingredients to room temperature. Bring the ingredients to room temperature before you whip up the frosting. This is especially important for the cream cheese-you do NOT want cold cream cheese, which can create a lumpy icing!
Sift the powdered sugar. Again, you want a beautifully smooth frosting! Sift the powdered sugar into the bowl when you make the frosting to eliminate any clumps.
Non-gluten-free. Use 2 cups of all-purpose flour for the oat and almond flours if you don't need to eat gluten-free.
Use gluten-free flour. If you wish, substitute 2 ½ cups of 1:1 gluten-free flour, such as Bob's Red Mill or King Arthur Flour, for the oat and almond flours, or use my homemade gluten free flour blend.
Stout substitute. If you don't drink alcohol, you could also try a non-alcoholic gluten-free stout. Another option is strong tea or coffee but I think if you can't do any kind of beer, it's probably best to make another cake recipe.