An instant house
This house is very quick.
1 mycelium
1 red mushroom
1 bonemeal
1 door
Dig 3 blocks down.
Place the mycelium.
Place the red mushroom on it.
Use bonemeal on it.
Dig out the pillar in the center.
Dig out 2 blocks in a vertical formation on any side of it.
Place the door in the opening.
Add any improvments you see fit.
Enjoy!