Help! Mushrooms growing in indoor plants!

Morbier

I've just been doing the rounds of watering my indoor plants and discovered some tiny mushrooms growing in one of the pots. Never seen this before and have been growing indoor plants and gardening for more years than I care to remember.

The pot (a large one) contains two Peace Lily plants, both of which I've had for ages. I re-potted them from separate pots about three months ago. I know that Peace Lilies don't like too much water, so they've been kept on the dry side, rather than too damp. They're in a darkish corner of the room as I know they don't like bright sunlight either. In fact, apart from sharing a pot, they're living under the same conditions as they always were.

The compost came straight from the bag, brand new multipurpose compost from my local garden centre.

What has happened?!

Jojo_the_Tightfisted

Mushroom compost.

Break them off and don't worry about it.