The liqueurs plus the sweetened condensed milk will give the brains their grayish color. Make sure that you don’t add the sweetened condensed milk until the gelatin mixture is room temperature. If you add it to hot gelatin mixture, then the milk may curdle.
Pour the vodka and liqueurs into a large measuring cup.
Sprinkle the gelatin over the liquors and allow it to bloom for 1 to 2 minutes.
Stir in the boiling water with a whisk until the gelatin has completely dissolved.
Allow the mixture to cool to room temperature.
Stir in the sweetened condensed milk.
Spray the brain molds lightly with nonstick cooking spray.
Fill the mold cavities halfway full of the brain gelatin mixture.
Cover the remaining gelatin with plastic wrap and set it aside to use later.
Refrigerate the molds for 1 hour or until the molds have set.