Process the strawberries and sugar in a blender or food processor until smooth, stopping to scrape down the sides as necessary. Press the mixture through a wire-mesh strainer into a medium bowl, using the back of a spoon to squeeze out all of the juice. Throw out the pulp.
Stir the vanilla and salt into the strained strawberry mixture then stir the strawberry mixture into the cold cashew milk.
Chill for at least 1 hour before serving. Store covered in the refrigerator for up to 3 days.
Prep time does not include the 60 minute inactive chill time.
The milk will separate as it sits, shake vigorously before serving.