Grease a 9 inch Springform pan, then line the bottom with parchment paper.
Heat together the Porter and butter in a small saucepan until butter is melted.
Place the sugar and cocoa powder in a large bowl and pour the hot butter and beer over the sugar mix. Whisk until the sugar has melted.
In a small bowl whisk together the eggs, sour cream and vanilla, then whisk this into the beer/sugar mixture until smooth.
Combine the flour, baking soda and cinnamon in medium size bowl.
Whisk the flour mixture into the beer/sugar mixture until smooth.
Pour the batter into the prepared Springform pan. Place in the pre-heated oven. Bake for 45-50 minutes or until a toothpick inserted in the middle comes out clean.
Remove the cake from the oven to a wire rack and let cool completely before removing from the Springform pan. It will take a couple hours to cool completely. Remove the cake to a serving platter.
Place the softened cream cheese in a large bowl and using an electric mixer, beat until fluffy. Gradually add the powdered sugar, alternating with the cream cheese and beat until smooth.