Soften Cream Cheese: Prepare the cream cheese by warming it up slightly to soften it. (I do this by heating it in a small dish in the microwave for 10 seconds or leaving it out on the counter for 15 minutes.)
Combine Ingredients: Measure ¾ cup soy milk and pour it into a Ninja Creami pint cup. Add the protein powder, cream cheese, maple syrup, and vanilla extract. Use a small wire whisk or fork to mix everything until well combined.
Add Milk: Add enough soy milk to the mixture to reach the max fill line on the pint cup. (About ¾ cup more.) Whisk again until everything is thoroughly mixed.
Long Freeze: Put the lid on the pint and place it in the freezer for at least 7 to 8 hours. (Tip: For an evening dessert, prepare it first thing in the morning.)
Spin to Consistency: Once completely frozen, remove it from the freezer and allow it to sit at room temperature for 5-10 minutes to soften a bit. Next, following the Ninja Creami manufacturer instructions, spin the mixture on "Ice Cream" mode. If it seems powdery, use the "Re-Spin" option. (If necessary, add a tablespoon of soy milk and continue to re-spin it until it reaches a creamy, ice cream-like consistency.)
Add Mix-ins: Add mix-ins, if desired. Make a small well in the center of the ice cream with a spoon and add small chunks of chocolate, fruit, or nuts. Select the "Mix-In" option.
Serve: To serve, scoop the ice cream into two bowls and enjoy! (Note: Half can be saved in the freezer for later but will have to be spun again.)