What's the actual way to grow mushrooms in minecraft?

if you ever find a mushroom fields biome, mooshrooms are the easy way. shear one and you get 5 mushrooms (it turns into a normal cow though).

dark is the main thing. place them on pretty much any solid block where the light is low (under a roof, in a cave) and they slowly spread. On mycelium or podzol they'll survive in any light. Want a lot fast? Bone meal one on dirt or grass with some room above it and you get a giant mushroom, break that for a stack.