I have always understood they grow where horses have been pastured. I would pick them, steam cook in the Microwave, and freeze for the winter.
You are very lucky.
I went to a village school, and the first thing I learned was not to tell anyone where the mushrooms are !

First make sure they are mushrooms and not toadstools!

if they are red with white spots.......... DO NOT EAT THEM!

If they look exactly like shop mushrooms beware. Pick one and bruise it. If it stains yellow its poisonous. If it has white gills don't eat it - the edible ones have pink gills that age to brown.

If they aren't the white ones don't do anything - they are just the fruiting bodies of a large underground plant that's feeding on something under the lawn. You can remove them if yu want to but they will be back next year. They will diappear by themselves in a few days. If you take a photo someone may be able to identify them for you but photo identifications aren't easy as you often need more info than appearance.

Foolproof advice for fungi is if you aren't sure leave it alone.

I previously answered a question that someone posted about toadstools in their lawn, and I think the answer is the same:

As far as I'm aware there are no fungicides available in the UK that are effective against fungi. However, since they are not damaging to the turf, and are part of a natural and temporary process and even beneficial for your lawn there is no need to treat them. In fact it's a sign of a healthy lawn.

They are not damaging to the turf and are a temporary problem.

As regards to mushrooms, if you are 100% sure that they are edible then harvest them while you can and be thankful for the unexpected crop :o)

My husband nearly cooked some we found in a garden and I persuaded him not to. We looked them up in our mushroom book and they were very like one which was poisonous. Thank goodness he didn't eat them. I on the other hand am allergic to mushrooms!

Thanks everyone for this advice. I just took it for granted they are Mushrooms. Thought the turf must have been cut from a field where there were horses the previous year.

I've been married 3 times and they all died. My first two wife's both died from eating poison mushrooms.

Ooh you story teller!!

Yeah, my 3rd wife died because she refused to eat her mushrooms. LOL.