Step 1: Making the Basic Shape
First you want to take a piece of tin foil about 3 feet long and crumple it up into the shape of a brain and try to compress it as much as possible
Step 2: Fixing It Up
Now you want to use Clay and try to fix the shape up a little bit so it looks more like the shape of a brain
Step 3: Sculpting the Texture
Now you want to roll little pieces of clay into small string things then you want to put them on twisting them and curling to make it look like the texture of a brain
Step 4: Painting
First you will want to put black paint on it and use a damp paper towel to wash it off so there is only black in the deeper areas of it then paint it with various pinks and reds to make it realistic.
I am sorry I forgot to take pictures of this step
Step 5: Enjoy
Do whatever you want with it like you could put it in a empty pickle jar or make a bigger one and wrap it up in cling wrap and put it in the fridge and maybe get a scare.
But just make sure you have fun!