Line a 9-inch springform pan with plastic wrap or foil. (This will make it MUCH easier to remove the tiramisu from the pan later on.)
Pour beer into a bowl. Dip one ladyfinger at a time for a second or two on both sides, then lay in the the prepared pan until the bottom of the pan is covered.
Spread half of filling over lady fingers. Dust with a thin, even layer of cocoa powder.
Repeat layers--ladyfingers, filling, and cocoa powder. Top with a third layer of lady fingers.
Pipe whipped cream on top of tiramisu and dust with a final layer of cocoa powder.
Cover and chill in the refrigerator for 4-6 hours, or overnight. (If you don't want to mess up the whipped cream or the top of your tiramisu, you can cover the pan with a large plate or lid.)
Remove from pan and cut into slices to serve!