In a mixing bowl, whisk together the heavy cream, whole milk, granulated sugar, and vanilla extract until the sugar is dissolved.

If making flavored ice cream, add the desired flavoring (chocolate syrup, pureed strawberries, or peanut butter) and mix well.

Pour the mixture into a freezer-safe container and freeze for at least 4 hours or until solid.

Remove the frozen ice cream base from the freezer and let it sit at room temperature for about 10 minutes to soften slightly.

Place the softened ice cream into the Ninja Creami bowl and process according to the manufacturer's instructions until creamy.

Serve immediately or transfer to a container and freeze for a firmer texture.