That's pretty crazy looking.. I have always been told mushroom growing in your soil is a sign of very healthy soil.
googling based on appearance and I think you have; "Leucocoprinus birnbaumii is a species of gilled mushroom in the family Agaricaceae. It is common in the tropics and subtropics. However, in temperate regions, it frequently occurs in greenhouses and flowerpots, hence its common names of flowerpot parasol and plantpot dapperling. It is considered to be toxic if consumed."