Pour 1 cup of the cold water into a medium bowl and sprinkle the gelatin evenly over the top. Let it sit for 2 minutes to bloom.

Heat the remaining 1 cup of water until hot but not boiling, then whisk it into the bloomed gelatin until fully dissolved.

Stir in the chia seeds, honey or maple syrup if using, lemon juice, vanilla extract, and salt. Mix well to combine.

Fold in the chopped berries if using, then pour the mixture into a shallow dish or silicone mold.

Let it cool at room temperature for 10 minutes, then refrigerate for 1 to 2 hours, or until fully set.

Slice into squares or scoop with a spoon and serve chilled.