In a small bowl, sprinkle the gelatin over 2 tablespoons water and let stand to soften and dissolve. In a medium saucepan, combine the cream, sugar, vanilla bean and seeds, and salt. Bring to a simmer over medium heat, then remove the saucepan from heat. Stir in the gelatin until fully dissolved. Add the yogurt, whisking gently until combined. Divide the mixture between six ramekins and cool to room temperature. Cover the ramekins with plastic wrap and refrigerate for at least 3 hours or up to 2 days. (You can also expedite the setting process by popping the ramekins in the freezer for 15 to 20 minutes.)
Just before serving, run a sharp knife around the edge of each ramekin and dip the ramekin base in a hot water bath for about 10 seconds. Invert the panna cottas onto individual plates. Serve garnished with crumbled lavender shortbread cookies on top!