Whisk sugar, gelatin, and salt in a small saucepan until very well combined.

Whisk in cream and let sit for 5 minutes.

Cut vanilla bean in half lengthwise. Using the tip of a paring knife, scrape out seeds. Add beans and seeds to the cream mixture.

Cook over medium heat, stirring occasionally, until mixture registers 150 to 160 degrees, about 5 minutes.

Remove from heat and let mixture cool to 105 to 110 degrees, about 15 minutes.

Strain cream mixture through fine-mesh strainer into medium bowl, pressing on the solids to extract as much liquid as possible.

Discard the remaining solids.

Gently whisk in buttermilk.

Set eight 5-ounce ramekins on a rimmed baking sheet. Divide the buttermilk mixture evenly among the ramekins. Invert the second rimmed baking sheet on top of the ramekins and carefully transfer to the refrigerator. Chill for at least 6 hours or up to 3 days (if chilling for more than 6 hours, cover each ramekin with plastic wrap).

Working with 1 panna cotta at a time, insert a paring knife between the panna cotta and the side of the ramekin. Gently run a knife around the edge of the ramekin to loosen the panna cotta.

Cover the ramekin with a serving plate and invert the panna cotta onto the plate. (You may need to gently jiggle the ramekin.)

Drizzle each panna cotta with honey, then top with berries and serve.