This is a healthier version of a traditional cobbler, with canola oil in place of some of the butter and whole-wheat flour instead of all-purpose flour. Unlike more classic biscuit-topped cobblers, the peaches and blueberries are nestled into a tender batter that swells around the fruit as it bakes. Other fruits may be substituted. It's especially beautiful when baked in and served right from a cast-iron skillet.