Make the cookie topping (optional): Stir together the crushed Nilla wafers and cinnamon in a small bowl. In a small skillet, melt the butter over medium heat. Stir in the cookie mixture. Continue to cook for another 2-3 minutes, until golden brown, then remove from heat. Transfer to a small bowl and stir in the granulated sugar. Set aside.
Make the Frappuccino: Add the ice to a high-speed blender, then pour in the cold brew, oat milk, toasted cinnamon syrup, ground cinnamon, and xanthan gum. Blend until smooth and no ice chunks remain.
Pour the frappuccino into a tall glass, then top with whipped cream and/or cinnamon crumble topping if desired. Drink up!
Notes
***Nutrition info does not include the cinnamon crumble topping. The topping recipe above makes 12 servings, about ¼ cup of topping.***Note the Nilla Wafers are not dairy-free or vegan. Swap in a dairy-free vanilla cookie of choice for a dairy-free crumble topping.