Make chervil oil In blender, purée oil and chervil until chervil pieces are very small, 2 to 3 minutes. Strain through fine-mesh sieve into small bowl, pressing on solids to extract all oil. Set aside. Make corn sauce In medium saucepan over moderate heat, warm oil. Add onion, carrot, celery, and garlic and sauté, stirring frequently, until vegetables begin to soften, about 7 minutes (adjust heat as necessary to keep vegetables from browning). Add stock and corn cobs, raise heat to moderately high, and bring to simmer. Lower heat to moderate and simmer, uncovered, 45 minutes, adding stock if most of the liquid evaporates. Remove from heat. Using slotted spoon, remove vegetables and corn cobs and discard. Add corn kernels to stock, raise heat to moderately high, and bring to simmer. Lower heat to moderate and simmer, uncovered, 15 minutes. While sauce is simmering, make chive potato hash In medium heavy skillet over moderate heat, heat oil until hot but not smoking. Add potatoes and sauté, scraping up browned bits every few minutes, until tender and golden brown, about 15 minutes. Remove from heat, stir in salt, pepper, and chives, and keep warm. Finish sauce Remove from heat and let cool slightly, then purée mixture in blender until very smooth, about 2 minutes. Strain through mesh sieve into large bowl, pressing on solids to extract all liquid. If sauce is too thick to pour, stir in a small amount of additional stock. Stir in salt and pepper and keep warm. Make scallops In small bowl, stir together coriander, salt, and chile powder. Rinse scallops and pat dry, then sprinkle both sides with coriander mix. In medium heavy skillet heat oil until hot but not smoking. Add scallops and sear until lightly browned and cooked to desired doneness, 2 to 3 minutes per side for medium rare. To serve, divide corn sauce among four plates. Top each pool of sauce with 1 tablespoon potato hash and 2 scallops. Drizzle with 1 teaspoon chervil oil and garnish with chervil sprigs.
