The recipe for Roast Squash and Sweet Potato Soup from Nigella's Christmas Kitchen (and the book Christmas, p53) is recommended for freezing. Does the soup need to be defrosted first or can it be reheated straight from frozen? Thank you.
Ideally frozen soups should be defrosted overnight in the refrigerator then reheated gently in a saucepan. However it is possible to reheat the soup direct from frozen and this is best done, at least partially, with a microwave. Transfer the frozen soup into a microwave-safe container, partially cover and microwave on low heat in 2 minute blasts until the soup has become slushy. Between each blast use a wooden spoon to try and break up the block of frozen soup slightly, so that it thaws evenly.
Once the soup has thawed to a slushy consistency you can add the marsala and either transfer it to a saucepan and reheat gently, or if you prefer to stick with the the microwave then reheat the soup by using 2 minute blasts on high power, stirring between each blast. With both methods please make sure that the soup is reheated until it is piping hot.