请问一个关于Bread and butter

都可以,但多数用is.
因为Bread and butter经常在一起连用,所以他们习惯说is,
类似还有fish and chips
e.g.Fish and chips is a popular take-away food which originated in the United Kingdom.

Would you like some more bread and butter?
再来一点黄油面包好吗?
Do not quarrel with your bread and butter.
【谚】不要砸自己的"饭碗"。
This bread and butter is too thick.
这片涂黄油的面包太厚了。

it depends on what you are using the term for. Bread and butter is another way of saying something is of necessity to a person. so you can treat the phrase as a single word, i.e. follow it with an s.
But if your only intent to use bread and butter to describe someone's dietary habit, then you should treat is as two words.

这是语法问题
翻译：面包和乳酪被西方人所亲睐
根据实际情况，西方人早餐一般是面包和奶酪，所以我们把bread和butter就看做是一个东西（早餐） 用is， 你可以翻下语法书 在“语法一致”那章去找

当and连结的两个名词是指同一个人或同一件事，and后的名词前没有冠词，谓语动词应该用单数形式；在and后面的名词前有冠词，谓语就用复数形式。例如：
The bread and butter is served for breakfast. 早饭供应黄油面包。
The bread and the butter are on sale. 正在出售黄油和面包。...