Add the sherry and cook for 5 minutes, scraping up the brown bits stuck to the bottom of the skillet.
Stir to scrape up brown bits from the bottom of the pan.
Add the remaining Marsala to the pan, stir to pick up any brown bits and pour over the chicken.
Add wine and bring to a boil, scraping brown bits off the bottom.
Sauté until onions are transparent, about 3 minutes, then add the stock, scraping up any brown bits.
Add the liquid and cook, stirring and scraping up any brown bits, until it is reduced by half.
Add wine, and stir to release any brown bits stuck to bottom of pan.
Say, if you wanted to paint a tree you'd probably make a brown bit down and a green blob on the top.
Increase heat to high, add wine, bring to boil, scraping up the brown bits from bottom of pan.
Increase the heat under the pan to medium and reduce the cooking juices, stirring up any brown bits, until they are thickened, about five minutes.