Spray your silicone brain mold lightly with cooking spray to ensure easy removal later.
In a mixing bowl, pour the gelatin mix and add the boiling water. Whisk vigorously for about 2 minutes until the gelatin is completely dissolved and the mixture is smooth and slightly thickened.
Add the cold water and vanilla extract to the gelatin mixture, then whisk again until fully combined. The mixture should be homogeneous and starting to cool slightly.
Pour the gelatin mixture slowly into the prepared silicone mold, filling it up just to the top. Tap the mold gently on the counter to eliminate air bubbles and help the gelatin settle evenly.
Place the mold in the refrigerator and allow the gelatin to set for at least 4 hours, or until completely firm and jiggle-proof.
Once set, gently invert the mold onto a serving plate. Carefully remove the silicone, revealing your creepy, brain-like gelatin sculpture.
Slice and serve, showcasing the textured, wobbly, and eerily realistic brain appearance. Enjoy the fun, spooky aesthetic during your Halloween celebration!