Mushroom and blue cheese omelet

A tortilla de patata—you see it everywhere as a stalwart of the tapas bars, of Spanish kitchens, and of pilgrimages like Andalusia’s boisterous El Rocio with its one million followers. Juanjo’s evolved version oozes flavor and should look like a golden pillow—before you slice into its velvety heart. Follow his example by playing with the ingredients, but make sure you have mastered the basic flipping technique.