Generally speaking, turning 21 involves heading out to bars and ceremoniously making up for 21 years of not drinking.

For a restaurant, it seems natural that it gets its own bar.

So say happy 21st to La Folie and welcome in La Folie Lounge, the boozy bar expansion of its classy, Michelin-starred French restaurant sibling, soft-opening Tuesday.

Where La Folie, the restaurant, is a four-star, white-tablecloth dining experience, the lounge will be versatile enough to act as both your special-occasion spot and also your neighborhood haunt—filling in the void of mellow lounges in Russian Hill.

Think of the lounge as a good mix of San Francisco minimalism and Moulin Rouge opulence: when you walk in, the Napoleon blue walls, pressed tin ceiling, metallic chandelier, plush ivory sofas and French trompe l'oeil panels make it easy to forget that this was the old La Boulange space.

Walk up to the leathery-tiled, resin-topped bar helmed by Casper Rice (Michael Mina, Rubicon), and you'll be downing classics with a French-inspired twist in no time (go for the elderflower liqueur-soaked Elder-Village Margarita or the Hangar One Buddha's Hand-spiked Andalusian Aperitif). Of course, you've learned not to drink on an empty stomach, so you won't want to miss Chef Passot's Lobster Croque Monsieur.

Think of it as a hot ham and cheese for over-21-year-olds…