Preheat oven to 450.
In a pot over medium high heat, add 4 cups berries (reserve 2 cups mixed berries for the end), 1/2 cup brown sugar, 1/2 cup powdered sugar, corn starch and beer. Allow to simmer until reduced and thickened, stirring occasionally, about 15 minutes.
Remove from heat, add reserved 2 cups of berries, stir to combine. Add to a deep dish pie pan.
In a bowl, add 2 tbs brown sugar, flour, baking powder, salt and stir to combine.
Add the butter, rub into the flour until well combined and resembles course meal.
Add the milk and 1/2 cup beer, stir until combined.
Gently add the flour topping, a bit at a time, to the pie pan until the berries are covered.
Bake at 450 until the topping has turned a light golden brown, about 18 minutes.
In the bowl of a stand mixer, add the cream, 1/2 cup powdered sugar and 2 tbs beer. Whip on high until soft peaks form, about 3 minutes.
Serve the cobbler topped with whipped cream.