In a medium pot over medium heat, cook cream, sugar, and salt, stirring frequently, just until sugar is dissolved, 1 to 2 minutes. (Do not boil.) Stir in vanilla.
Transfer cream mixture to a freezer-safe container (preferably plastic). Freeze until cold but not frozen, 1 to 2 hours.
Using a handheld mixer on medium-high speed, whip until cream until stiff peaks form (this will take 7 to 10 minutes). Drizzle with milk and fold until combined.
Return soft serve to freezer and freeze until firm, 2 to 4 hours more.
Transfer soft serve to a piping bag fitted with a large star tip (if desired) and pipe into cones. Top with sprinkles (if using).
