It looks like Mr Bill stuck in a pizza crust by Mr Hand....

You're bad!!
what do you have them growing in?
The substrate is used coffee grounds and vermiculite. All the white stuff is the mycelium which is like the roots of the mushroom. Basically you make your substrate it can be about anything, then you innoculate it with either grain/dowel spawn, spores, or mycelium(liquid culture or agar wedges), then it will grow and take over the substrate.
Grain/Dowel Spawn to substrate = immediate mycelium growth
Liquid Culture/ Agar wedges to substrate = immediate mycelium growth
Spores to substrate = germination process then mycelium growth
Moisture is important as is temperature, container or substrate is really endless possibilities. You simply need substrate with nutrients in it for the mycelium to eat. Wood, coffee grounds, brown rice flour, cellulose, straw, manure, wild bird seed, rye berries/seed, popcorn kernels, really about anything.
Oysters are the easiest, fastest, most forgiving to grow. I messed up a lot on my experiment which is why it has taken 2.5months and im only just now getting mushrooms....but i'm still getting mushrooms!! I didnt keep the substrate wet enough, i didnt use a good container, i didnt air out the CO2, i put them in a place that was to cold, then in a place that was way to hot, etc.....yet here they are growing mushrooms.
Today's updated picture is from DH(i forgot to take one before i left the house)
24hrs after the last picture
DH took the picture from a different angle and his camera isnt as good as my phones but i'm pretty sure it is obvious how much that one mushroom has gown. That little straight up and down mushroom to just to the left of the monster mushroom.....was the smaller boy looking one from yesterday's picture.