Mushrooms sprouting overnight

I am in awe of how fast things grow. My avocado tree sprouted overnight and grew visibly each day. My mushrooms are now doing the exact same thing.

Here is what they looked like when I started.

Day 0
Nothing happens for a few days and I wonder if I messed something up.

Day 4
All of a sudden, white growth happens in the corners.

Day 5
And then the mushrooms start growing.

Day 6
It is supposed to take 10 days for these mushrooms to grow big enough to harvest and eat. I don't doubt it! I can't wait to see what they look like when I get up in the morning.