In a small bowl, sprinkle the gelatin over the cold water and let it sit for about 5 minutes to bloom.

In a medium saucepan, combine the heavy cream, whole milk, sugar, instant coffee granules, vanilla extract, and salt. Heat the mixture over medium heat, stirring occasionally, until the sugar and coffee granules are dissolved and the mixture is hot but not boiling.

Remove the saucepan from heat and stir in the bloomed gelatin until fully dissolved.

Pour the mixture into individual serving cups or ramekins. Allow them to cool to room temperature, then cover and refrigerate for at least 4 hours or until set.

To serve, run a knife around the edge of each panna cotta and gently invert onto a plate, or serve directly in the cups.