Here is a really easy way to make a brain for your holiday decorations. If cooked properly and let sit out to congeal in the appropriate sized bowl this mass of noodles feels just hard and wet enough to give the shivery impression that your holding a brain. Being made of flour, the noodles stick together rather well, so it can stand up to minor handling, I wouldn't pass this around the room, but you could carry it around for a while.
First thing you need to do is dust off your favorite pasta recipe. I use 2 cups of all purpose flour, 2 eggs, and just enough water to bind it together (water as needed while kneading)... Of course, if you want a white pasty looking brain, then this recipe will work, but if you want a brown looking brain with bits of dark lesions you need to add a little something extra to the mix.
My secret recipe is dehydrated tomato paste... If you spread out tomato paste on a dehydrator sheet and cook it down to a fruit leather, you can grind up the sticky bits in a food processor. You will need to make the majority of the tomato leather into a powder, but you will also want to leave some small chunks to imitate zombie lesions.
Dump the flour and tomato powder in a bowl and mix well, then make a impression in the center and crack the eggs into it.
Mix the eggs with a fork, and gradually scrape in the flout until you end up with a ball of dough, if the mixture is not moist enough, add in water as needed, just a little at a time.
Next knead the dough until it changes to a firm smooth ball. You really need to work the flour gluten well - 15 minutes or so will probably be the right amount.
After you have a firm ball of dough, roll it out as thin as possible. If you can keep the dough in a rectangle the next step will be easier.
After you have the dough as thin as you can make it, flour it lightly if needed, and roll it into a tube.
But strips of noodles off the tube, and unroll.
Dump the noodles in to a boiling cauldron of salted water.
Cook for a couple of minutes until it is cooked, but not mushy. I think almost al dente is about right.
Strain the water and dump the noodles into a bowl sized slightly smaller than the head you wish to fill.
Let sit out at least 20 minutes for the water to evaporate and the noodles to paste together.
Flip the bowl onto your plate. You can shape it a little to get the perfect brain shape.
If you repeat this again, you can end up with two hemispheres of the brain.
Enjoy, with bloody marinara if desired...