Grilled ears of corn, caked in butter, lime juice, and chili powder, are one of summer's greatest, messiest backyard treats. But for gatherings that merit food with more finesse, Brian Roche of Boston's Lolita Cocina & Tequila Bar has translated that winning Mexican formula into an elegant bisque. He keeps the ingredient list short, letting the corn's flavor sing loud and clear. The recipe does call for a good pinch of sugar, but if you're using corn that's especially sweet, you may not even need it.