Preheat oven to 350°F. Grease 3: 8-inch round pans, dust well with cocoa powder. Alternately, baking spray with flour may be used. Be sure to coat the pan well. Line the bottom of each pan with parchment paper. Set aside. 

In a large bowl or stand mixer, cream together butter and sugar, beating until light and fluffy. Mix in eggs one at a time, followed by vanilla, salt and baking soda. Add cocoa powder, mixing on low until fully combined. Add half of the flour, mixing until combined. Slowly mix in half of the beer, followed by half of the sour cream. Repeat with remaining flour, beer and sour cream. Divide batter equally between prepared pans. Use a small offset spatula to spread batter into an even layer. *(see note)

Bake cakes at 350°F for 30-40 minutes or until a toothpick inserted comes out clean or with just a few moist crumbs. Cool in pan on a wire rack until easy to handle. If necessary, carefully run a sharp knife or metal spatula around the edge of the cake prior to removal. Place a parchment lined wire rack over each cake. Invert and carefully remove cake. Cool completely. 

Wrap room temperature cakes with plastic. Chill until ready to proceed. Cakes may be made up to 3 days ahead. 

In a large bowl or stand mixer, beat cream cheese until smooth. mix in butter, followed by vanilla and cinnamon. Mix in brown sugar until just combined. Add 1 cup of powdered sugar at a time, mixing well between additions. 

If necessary, level off and remove any dome from chilled cakes with a serrated knife. 

Transfer first cake layer to desired serving tray or cake stand. Top off with 3/4 cup frosting. Use an offset spatula to spread frosting into an even layer. Top off with second layer and repeat. Finally add third layer. Add a thin layer of frosting to the top and sides. Chil for 1 hour. 

Cover frosting until ready to proceed. 

Cover cake with remaining frosting, smoothing out with a bench scraper or offset spatula. Use a spoon or spatula to create a swirl on the top. 

Chill cake for at least 1 hour or until ready to serve. This will help the frosting to set. 

Store cake in an airtight container, chilled or at room tempertture, for up to several days.