Sprinkle the unflavored gelatin evenly over the cold water in a small bowl. Let it bloom for 5 minutes without stirring. The gelatin will absorb the water and become spongy.
In a medium saucepan, combine the heavy cream, whole milk, honey, and dried culinary lavender. Heat over medium heat, stirring occasionally, until the mixture just begins to simmer. Do not let it boil.Remove the saucepan from the heat, cover, and let the lavender steep for 10 minutes to infuse the cream.
Strain the cream mixture through a fine mesh sieve into a clean bowl, pressing gently on the lavender to extract as much flavor as possible. Discard the lavender.
While the cream is still very warm, add the bloomed gelatin, vanilla extract, and salt. Whisk gently until the gelatin is completely dissolved and the mixture is smooth.
Divide the mixture evenly among 6 ramekins or small glasses. Let them cool at room temperature for 15 minutes, then cover and refrigerate for at least 4 hours or overnight until fully set.
Serve the panna cotta chilled, topped with fresh berries. If using ramekins, you can briefly dip the bottom in warm water for a few seconds and invert onto a plate to unmold.