In a hot skillet, coat with 1 tablespoon of fat and sautee leeks until soft, about 6 minutes. Season. Deglaze with white wine and completely reduce. Set leeks aside, wipe out pan and heat again. Add remaining fat and sear potatoes brown, about 10 minutes. Add back the leeks and chervil. Move around quickly to heat thoroughly. Check for seasoning.
PLATING On the plate with the liver, place hash to the side and ladle sauce on the liver.