Idiomatic expressions using food are abundant in English - and probably every other language as well, given food's importance to our lives. Many of these have been borrowed from a tasty web-site called usingenglish.com
About as useful as a chocolate teapot
Someone or something that is of no practical use is about as useful as a chocolate teapot.
Alike as two peas
If people or things are as alike as two peas, they are identical.
All the tea in China
If someone won't do something for all the tea in China, they won't do it no matter how much money they are offered.
All your eggs in one basket
If you put all your eggs in one basket, you risk everything at once, instead of trying to spread the risk. (This is often used as a negative imperative- 'Don't put all your eggs in one basket'.)
Apple of your eye
Something or, more often, someone that is very special to you is the 'apple of your' eye.
As cool as a cucumber
If someone is as cool as a cucumber, they don't get worried by anything.
Back to the salt mine
If someone says they have to go back to the salt mine, they have to return to work.
A person who cannot be trusted is a bad egg. Good egg is the opposite.
Banana republic is a term used for small countries that are dependent on a single crop or resource and governed badly by a corrupt elite.
(UK) A banana skin is something that is an embarrassment or causes problems.
If something bears fruit, it produces positive results.
Best thing since sliced bread
If something is the best thing since sliced bread, it is excellent. ('The greatest thing since sliced bread' is also used.)
(USA) The Big Apple is New York.
The big cheese is the boss.
Bread and butter
Bread and butter issues are ones that affect people directly and in a very important way.
Used to describe the person that earns the most money. For example - She's the breadwinner in the family.
Bring home the bacon
A person who brings home the bacon earns the money that a family live on.
Butter wouldn't melt in their mouth
If someone looks as if butter wouldn't melt in their mouth, they look very innocent.
Cake's not worth the candle
If someone says that the cake's not worth the candle, they mean that the result will not be worth the effort put in to achieve it.
Carrot and stick
If someone offers a carrot and stick, they offer an incentive to do something combined with the threat of punishment.
Chalk and cheese
Things, or people, that are like chalk and cheese are very different and have nothing in common.
Cheap as chips
(UK) If something is very inexpensive, it is as cheap as chips.
If people cherry pick, they choose things that support their position, while ignoring things that contradict it.
Chew the cud
If you chew the cud, you think carefully about something.
Chew the fat
If you chew the fat with someone, you talk at leisure with them.
Cook up a storm
If someone cooks up a storm, they cause a big fuss or generate a lot of talk about something.
A couch potato is an extremely idle or lazy person who chooses to spend most of their leisure time horizontal in front of the TV and eats a diet that is mainly junk food.
Crack a nut with a sledgehammer
If you use a sledgehammer to crack a nut, you apply too much force to achieve a result. ('Jackhammer' is also used.)
Cream of the crop
The cream of the crop is the best there is.
Crème de la crème
The crème de la crème is the very best of something.
(UK) If something is a bit of a curate's egg, it is only good in parts.
If people try to curry favour, they try to get people to support them.
Cut the mustard
(UK) If somebody or something doesn't cut the mustard, they fail or it fails to reach the required standard.