Add the remaining oil and another tablespoon butter to the pan and heat over high heat. Add the livers and sauté quickly until very pink in the center but not rare. Using a slotted spoon, add the livers to the onion mixture. Pour the Calvados into the pan, simmer a minute or two, scraping loose the browned bits, and add to the livers. Cut the remaining
Line the bottom of a
To serve, dip the bottom of the pan in hot water, then invert the mousse onto a platter. Cut into slices and serve with croutons, apple slices, and some greens tossed with a little Walnut Vinaigrette, or simply with toast or croutons.