Microwave the cream cheese in a heatproof bowl for about 10 seconds until softened. If you don't have a microwave, let it sit at room temperature for 20 to 30 minutes.

Spoon the softened cream cheese into a medium mixing bowl.

Add the maple sugar and vanilla extract to the bowl.

Beat the cream cheese, maple sugar, and vanilla together with an electric mixer or whisk until smooth and no lumps remain.

Pour in the heavy cream and whisk constantly to help the sugar dissolve into the cream.

Add the whole milk while continuing to whisk.

Keep whisking until the maple sugar is fully dissolved and the mixture is well combined.

Pour the ice cream base into a Ninja CREAMi pint container, staying below the max fill line.

Place the lid on the pint and freeze on a level surface in a deep freezer for 24 hours.

After 24 hours, remove the pint from the freezer and assemble it in the Ninja CREAMi machine according to the manufacturer's instructions.

Set the machine to the full Ice Cream blend program and let it churn the ice cream.

When the cycle ends, remove the pint and take off the lid.

Use a spoon to scoop out a hole in the center of the churned ice cream, about 1 1/2 inches wide and 2 inches deep.

In a small bowl, toss the chopped walnuts with the maple syrup, soy sauce, and crushed red pepper flakes. Reserve 1 tablespoon of the mixture for serving, then spoon the rest into the center hole.

Place the lid back on the pint and return it to the machine.

Run the Mix-in cycle so the machine folds the spiced walnut mixture through the ice cream.

Remove the pint, scoop the ice cream into bowls, and garnish each serving with the reserved spicy umami maple walnut topper.

Store any leftover ice cream in an airtight container in the freezer for up to 2 weeks.