Mix the base: In a Ninja Creami pint container, add the protein powder, cocoa powder (if using), peanut butter, vanilla, xanthan gum (if using), salt, and sweetener (if using). Fill with plant-based milk to just below the fill line (about 2 cups). Mix thoroughly using a whisk, fork, strong milk frother, or immersion blender until fully combined and smooth.
Freeze flat: Freeze uncovered for 24 hours, or until fully solid. This helps the base freeze evenly and avoids humps. Once frozen, you can pop the lid on if storing longer.
Spin it: Remove from the freezer and run the outside of the container under hot water for 1–2 minutes to help prevent icy edges. Insert into the Ninja Creami and select the 'Lite Ice Cream' setting.
Re-spin if crumbly: If the texture is dry or powdery, add a splash (1–2 tablespoons) of plant-based milk and press 'Re-spin.' Repeat if needed until creamy.
Add toppings: After the final spin, drizzle with extra peanut butter and top with your favorite add-ons. Vegan peanut butter cups, roasted peanuts, chocolate chips, peanut butter chips, or a drizzle of chocolate syrup.
