As they gear up to toast their 20-year partnership, which started with Champagne salon Narcisse, Kathryn Sullivan Alverà and Jason Clark (who also operated bubbly boîtes Prosecco and Domaine) simultaneously prepare to debut another Champagne-fueled concept: Marchesa (535 N. Wells St., River North) will fuse Continental cuisine with a roster of still and sparkling wines, and it’s set to pop its first corks in May.

The 6,500 square-foot former Crofton on Wells digs will house Marchesa’s three levels. At its base lies an intimate, subterranean “Champagne Cave” with a fireplace, barrel-vaulted stone walls, and gilded accents. Sullivan Alverà and Clark secured special permits to store wines beneath the sidewalk, allowing for primo temperature and humidity control for sommelier John Cressman’s most special stuff.

On the main level, a chinoiserie-inspired bar and a kitchen with a chef’s table will sport jewel-tones, sculptural furniture, and dramatic light fixtures. Cressman will offer Champagnes, plus a lengthy selection of Old World and New World wines by the glass, half bottle, bottle, and magnum.

The upstairs space is designated for private dining, and its decor will mimic a lavish Paris apartment. It all sounds très fancy, but Sullivan Alverà says that’s not the M.O. “We’re trying to create a home that has opulence but is comfortable,” she promises.

Mark Sabbe (Mercat a la Planxa) will cook up his takes on Continental classics from France, Italy, and Spain. “We’re doing Continental [cuisine] because we want a broad canvas to paint on instead of focusing on one region or country,” Sullivan Alverà says. Starters will run the gamut from French-style hors d’oeuvres and canapés to Italian antipasti to Spanish pinxtos and tapas. Sabbe plans for oft-rotating pastas, paellas, and risottos; the latter of which will feature asparagus, Meyer lemon zest, and mascarpone on the opening menu. Oh, and tableside-shaved truffles, Petrossian caviar, and medallions of foie gras will be mainstays.

Not to discount Sabbe’s culinary prowess or Cressman’s wine expertise, Sullivan Alverà says Marchesa isn’t about the rockstar staff: “Restaurants have all become chef- and bartender-driven. We are trying to do a guest-driven restaurant. Chefs can come and go. [We want to] make the guest feel like the star,” she says.