Add the almond milk, soy milk, strawberry protein powder, salt, and xanthan gum (if using) to a Ninja Creami pint container. Use an immersion blender to blend everything together until smooth and fully combined.
Add the frozen strawberries to the pint container, pressing them down as you go. Continue adding strawberries until the mixture reaches the max fill line—do not exceed it! The amount of strawberries needed will vary depending on the size. Make sure no strawberries are sticking up above the mixture; the top should be flat.
Place the pint container in the freezer and freeze for at least 24 hours, until completely solid.
Process using the Lite Ice Cream setting on your Ninja Creami.
If the texture is crumbly after the first spin, add 1–2 tablespoons of plant milk and run the Re-spin function until smooth and creamy.
Optional: Make a hole in the middle of the creami all the way to the bottom and add in 2-3 fresh strawberries. Run the Mix-in setting.
Divide into two servings and enjoy immediately with your favorite toppings.