By LOUISE DIXON LONDON — Winter has set in, the Christmas lights have been switched on, and London’s top cocktail bars have added their seasonal favorites to bar menus. From a festive Old-Fashioned to a boozy hot chocolate, these after-dinner drinks might inspire your own menu of holiday cocktails, to be supped slowly by the fire or washed down with your Christmas pudding. Five bars share their recipes: ROASTED CHESTNUT OLD-FASHIONED, from Archive & Myth This hidden speakeasy, accessed by a password-protected door, has updated the traditional Old-Fashioned.