Heat a frying pan big enough to hold the liver in one layer over a medium flame. Add a little olive oil, season the liver and cook on one side for 3 minutes. Turn and give the other side 2 minutes. You may not have a frying pan large enough to hold the liver in one go, in which case cook in two batches keeping the first warm in a 110°C/225°/F/Gas ¼ oven. Wipe the pan after the first batch, and add more oil. (Saves washing-up!)
Remove the liver from the pan and transfer to a warm serving plate. Add the Marsala and vinegar to the pan, turn up the flame and boil down until syrupy. At this point add the butter in pieces, off the heat, then shake the pan until the butter is incorporated into the sauce. Pour over the liver and serve. The whole process of making the sauce should only take a minute or so.
© 1996 Alastair Little. All rights reserved.