Preheat oven to 400.
In a processor add flour, baking powder, baking soda, salt, and sugar.
Pulse to combine. Add the cold butter, process until well combined. Add to a large bowl.
Add the buttermilk and beer. Mix with a fork until just combined.
Add to a well-floured flat surface, pat into a rectangle. Using a cold rolling pin (preferably marble) gently roll into a large rectangle, about 3/4 inch in thickness, using as few strokes as possible.
In a medium sized bowl add the softened butter, brown sugar, white sugar, cinnamon, nutmeg and pinch of salt. Stir until a paste forms.
Spread the dough with the butter mixture. Starting at the long end, roll into a tight log. Cut 2-inch rounds, place in a baking dish.
Bake at 400 for 12 to 15 minutes or until the tops are golden brown.
Allow to cool.
Stir together the powdered sugar, buttermilk and vanilla until well combined. Serve the biscuits topped with icing.