The way to get mushroom blocks is really simple. All you have to do is find a really dark spot and place a mushroom. It can be placed on any block which is really sweet! The room should look this dark or maybe slightly darker. Once it has grown, it should look like this. A quicker way to grow it is by using bonemeal. Note: When you're breaking the blocks, only use godded items because you need silk touch to collect it. Hopefully this tutorial helped you if you wanted mushroom blocks. -Diamond_Slime12
Should add that you need to use bonemeal. Also, the specific light level needed is 4 or less to place it, however once placed you can bring the light level as high as you wish. And if you have mycelium it can be placed at any light level