Cut vanilla bean in half lengthwise. Using tip of paring knife, scrape out vanilla seeds. Combine vanilla bean and seeds and cream in medium saucepan and bring to simmer over medium heat. off heat, cover, and let sit until flavors meld, about 10 minutes.

Sprinkle gelatin over water in bowl and let sit until gelatin softens, about 5 minutes. Fill large bowl halfway with ice and water. Set four 4-to 5-ounce ramekins on rimmed baking sheet.

Whisk gelatin mixture, erythritol, and salt into cream until dissolved. Transfer mixture to bowl and set over prepared ice water bath. Stir mixture often until slightly thickened and mixture register 50 degrees, about 20 minutes. Strain mixture through fine-mesh strainer into 2-cup liquid measuring cup, then divide evenly among ramekins. Cover all ramekins on baking sheet with plastic wrap and refrigerate until panna cottas are just set and wobble when shaken gently, at least 4 hours or up to 12 hours.

To unmold, run paring knife around perimeter of each ramekin. (If shape of ramekin makes this difficult, quickly dip ramekin into hot water bath to loosen panna cotta.) Hold serving plate over top of each ramekin and invert; set plate on counter and gently shake ramekin to release panna cotta. Top with strawberries and mint. Serve.