Stout is the last thing to be poured into the Root Beer Float at Lord Hobo, creating a foamy cascade that helps give this cocktail its name. Made of Sailor Jerry rum, draft stout, Pepsi, and — the key ingredient — a birch-bark liqueur called Root, nestled over ice, the Root Beer Float sounds like a car crash, but it’s delicious. Try it with parmesan-dusted truffle fries at this cozy, noisy Cambridge pub. Who needs ice cream?