“She’s someone who wants things to be very, very sophisticated and elegant,” Lawrence says of the vivacious mother of three. “It doesn’t look like a super-casual, of-the-moment home—this is definitely more classic and grown-up.” The pair focused on seamlessly integrating McCormick’s art collection and inherited furniture (she’s a descendent of William Deering and of Cyrus McCormick, who invented the mechanical reaper and revolutionized modern farming), with new acquisitions and their own bespoke creations.

They gut-renovated McCormick’s fifth-floor primary suite down to the studs, moving the bedroom to the south side of the 18-foot-wide home, cloaking the bathroom in blue-quartzite panels inspired by the garden court of the Frick Collection, and devising a show-stopping dressing room—complete with a gleaming silver leaf ceiling. The stairways and corridors of the 8,500-square-foot home were changed from a “margarine yellow” to a glamorously lacquered black–and–pearl white, a nod to Coco Chanel’s original Parisian store. Garciavelez and Lawrence reimagined the dining room as a gilded forest, papering the walls with de Gournay’s handmade chinoiserie blossoms and nesting treelike candelabra atop two 1950s Maison Jansen writing desks, cleverly repurposed as dining tables. “They just fit the bill in the most magical way,” says Lawrence, explaining that the desks can be separated for intimate supping or pressed together for grand entertaining—a moveable feast.

The living room, meanwhile, became a home gallery, displaying McCormick’s impressive art holdings (including an 1876 John Singer Sargent portrait of her great-great-grandfather Charles Deering, previously on display at The Art Institute of Chicago) above an amorphous travertine-and-bronze Franck Evennou table and a curving royal blue sofa, designed by Carlos David in decadent silk velvet and leather.

“You have that juxtaposition—it’s unexpected,” notes Garciavelez. “The table is a classic purchased piece, and the sofa is designed by us, but there’s this sense of communication between them.” As Lawrence summarizes, “Every decision, crevice, corner, nuance, moment is 1,000% considered.”

Including the sixth-floor terrace (designed by Harrison Green), where last July, after completing the renovations, the couple got engaged. “It sounds a little hippy-dippy,” says Lawrence, “but I really think so much of what goes into our work—and the ultimate outcome—is a product of joy and, to some extent, love.”

“How do you create the perfect princess room for a 10-year-old?” Lawrence asks. “A pink-and-gray canopy bed and an over-the-top print on the blankets and pillows,” Garciavalez answers. The ferocious tiger-striped throw and pillows are by Saved NY—in 100% cashmere, naturally.