Roll a piece of fondant into a ball slightly smaller than a walnut. Press down on one end of the ball to flatten it slightly and create an oval shape.
Take a palette knife or other tool and gently press down in the middle across the top of the brain, lengthways. This creates the 'right side' and 'left side'. Don't press too hard, as you don't want to cut through the fondant.
Take another piece of fondant and roll into a thin rope.
Starting on either the left or right side, press the fondant rope onto the brain in an 'S' fashion, working lengthways from top to bottom. Once you've finished one side, start the other. Roll more rope if needed.
Once your brain is covered, it is all set! Just let it rest before using. If desired, you can use a bit of red food colouring mixed with golden syrup to paint on 'veins'.