Preheat the oven to 350°F or 180°C and line a muffin tin with cupcake liners.
Add the butter, dark chocolate, granulated sugar, dark brown sugar, and vanilla extract to a medium-sized pan and melt it on the stove over low heat. Stirring continuously with a wooden spoon or rubber spatula.
Once everything is melted, take the mixture off the heat and let it cool for about 15 minutes.
Separate the egg whites from the yolks. Put the egg whites in a medium-sized bowl and set aside.
Add the egg yolks, Baileys, shredded almonds, and flour to the melted chocolate mix. Mix with a wooden spoon until well incorporated.
Beat the egg whites with a hand mixer (or stand mixer) until stiff peaks form.
Carefully fold the stiff egg whites into the chocolate mix using a rubber spatula or a wooden spoon. Be careful not to over-mix; you will lose all the air in the egg whites, and the batter will get runny.
Use a cookie scoop and add the batter to the lined muffin tin. Fill the liner to about 3/4 full.
Bake for 18-20 minutes.
Let the cakes sit at room temperature for 5-10 minutes before taking them out of the muffin tins and onto a cooling rack. Make sure the cupcakes are completely cooled before starting to add the buttercream. Even if they are just slightly warm, the buttercream will melt right off.