Homogenize brain in a blender with cryoprotectant. Pour into a brain shaped mold and freeze. It penetrates cell membranes 20 times as fast as glycerol. Pretend that cryoprotectant perfusion was done and do the usual slow freeze. The result is hamburger.
Microwaves can rapidly penetrate and fix tissue.
Pack the brain with ice and place in a microwave with a turntable, which has been top rated by Consumer's Reports for uniformity of heating. Cook using pulses of radiation until well done. Treat brain with cryoprotectants by storing it in a concentrated cryoprotectant solution for a week. Store in freezer until needed. Freeze brain slowly to -10 C to limit ice crystal damage.