In a large mixing bowl, measure out the Rice Chex cereal and set aside.
In a microwave-safe bowl, combine the white chocolate chips and vanilla extract. Microwave in 30-second intervals, stirring in between, until melted and smooth.
Pour the melted chocolate over the Rice Chex cereal and gently fold until all the cereal is evenly coated.
In a separate bowl, mix the crushed freeze-dried strawberries, powdered sugar, strawberry cake mix (if using), and a pinch of salt.
Transfer the coated cereal to a large resealable plastic bag or a large bowl. Add the strawberry mixture and shake or stir until the cereal is well coated.
Spread the puppy chow on a baking sheet lined with parchment paper to cool for about 30 minutes.
Once cooled, serve immediately or store in an airtight container for up to a week.