What do you do if you want a quality dessert around midnight but don't want to get gussied up and spend a fortune at some South Beach hot spot? For 46 years Rascal House has had the answer. The place is open until at least 1:00 a.m., and the waiters here wouldn't bat an eye if you sauntered into the joint in your bathrobe as long as you had your wallet with you. At best they might offer an acerbic comment in the gruff manner for which they are famous, as they wait for you to choose from among the 34 different homemade treats. Dessert at Rascal House is meant to satisfy rather than dazzle. There are no effete dribbles of exotic sauces or bizarrely flavored sorbets. The favorite here is the cheesecake, rich and heavy enough to be a meal in itself. If your arteries can take it, move on to the bobka, a marbleized pound cake, or the Victory layer cake, which consists of seven levels of chocolate and whipped cream. Don't worry about offending your fellow patrons: There is no shame in being a glutton in this cafeterialike setting.