Preheat the oven to 350º F.

In a large mixing bowl, whisk together the cocoa, sugar, flour, baking soda and salt.

In another medium-size mixing bowl, combine the beer, butter and vanilla and mix well. Add the eggs one at a time. Mix in the yogurt and whisk well. Combine the wet and dry ingredients and mix until smooth.

Lightly grease or line 24 muffin tins. Divide the mixture evenly between the muffin tins, filling each 3/4 of the way full. Bake in the middle of the oven for 12 -14 minutes and then rotate the pans and continue to cook for 10 to 12 minutes longer. Cool completely in the pan.

In a large bowl or the bowl of a standing mixer, beat the cream cheese and the butter using the paddle attachment, until smooth. Add the confectioners' sugar and continue to beat until the mixture is smooth and creamy. Add the Bailey's Irish Cream and beat until well mixed. The icing can be used immediately or stored in the refrigerator for several days. Allow to come to room temperature before using.