Strawberry Panna Cotta with Strawberry Compote

Blend strawberries, buttermilk, and sugar in a blender until very smooth, then pour through a very fine sieve into a medium bowl, pressing hard on solids. Discard solids. Sprinkle gelatin over milk in a small bowl and let stand 1 minute to soften. Bring cream to a boil in a small saucepan. Remove from heat and add gelatin mixture, stirring until dissolved. Whisk cream mixture into strawberry purée and pour into molds. Chill molds, covered, until firm, at least 8 hours. To unmold, dip molds in a small bowl of hot water 2 or 3 seconds, then invert panna cottas onto dessert plates and remove molds. Let stand at room temperature 20 minutes to soften slightly.