Gratin typically brings to mind a rich and cheesy dish of root vegetables (pronounced by all American children to rhyme with “all rotten”).  Nutritional guilt over this fat fest drives food bloggers to frantic rearrangements of their refrigerator poetry magnets into epithets like “a holiday indulgence” and a “once in awhile treat.”  But in the Adams-Rivard kitchen we scoff at a such reservations.  We eat gratins when we feel like it, whether Santa Claus or the Easter Bunny is joining us for dinner or not. Thank God for bicycles.  Which offers me a segue into this week’s dish, Eggplant, Pepper and Tomato Gratin.  While pedaling through Provence a month ago we couldn’t help but notice how much lighter a Provencal gratin is than its Gerard Depardieu-like cousins to the north.  The cream had vanished, along with much of the cheese, both supplanted by olive oil, bread crumbs, and fistfuls of crushed herbs.  Olive oil, we were reminded, transforms the flesh of vegetables into something unctuous.  Caramelization is the gilding on the lily.