下面一段摘自 2018全国卷Ⅱ，不太理解 soft-serve 的意思和构成方法，请专家老师讲解一下：

If you have a juicer, you can simply feed in frozen bananas and some berries or sliced fruit. Out comes a “soft-serve” creamy dessert, to be eaten right away. This makes a fun activity for a children’s party; they love feeding the fruit and frozen bananas into the top of the machine and watching the ice cream come out below.