マッシュポテトって英語でなんて言うの？

People usually use "mashed potato" but you can also use "puree", especially if it is instant from a box.

Mashed potatoes are potatoes that have been boiled and then crushed into a soft pulpy mass.
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We had beef and mashed potatoes for dinner.

In the UK, people love to eat 'mashed potatoes!' Sometimes we just call it 'mash'.
For example, 'bangers and mash' is sausages and mashed potato.

Sometimes we call it creamed potato.

A popular dish in the UK is 'Bangers and mash'. Bangers are fried or grilled sausages and they are usually served with mash, gravy, onions and baked beans.

This is made by boiling potatoes, peel of the skin and mash them with milk,butter and salt. You can serve them with any meat of your choice.

It is potatoes that have been boiled , crushed into a soft mass, typically with the addition of butter and milk.
Example -"dinner was always steak pie and mashed potato, with soup to start and trifle to finish"

I hope this helps :-)

We would call that mashed potatoes. If it came from a package where you just add hot water or similar, it would be 'instant mashed potatoes'. If there is some sort of spice or flavour, we could add that name, for example: 'garlic mashed potatoes'.

This is a dish of potatoes that have been peeled, boiled until
soft and then mixed until smooth with milk, butter and salt.
It can be topped with nutmeg, parsley or mixed herbs.

Mashed potato is a perfect side dish with different menus. Mashed potato with butter andsalt, or the more exotic mashed potato with rosemary and garlic can be divine!
In India we call this dish Aloo Bharta...or mashed potato Indian style!
Not all potatoes are good for mashing! Sometimes different kinds of potatoes are mashed together as they taste better that way!

This can be referred to as:
"mashed potato"
"mashed potatoes"