Preheat the oven - Preheat the oven to 350°F (175°C).

Mix the wet ingredients - In a large mixing bowl, cream 1/2 cup (1 stick) of softened butter with 1/2 cup of granulated white sugar and 1/4 cup of light brown sugar until light and fluffy. Add 1 large egg and beat until smooth.

Add the dry ingredients - Add 1 1/2 cups of all-purpose flour, 1/2 teaspoon of baking powder, 1/2 teaspoon of cream of tartar, and the contents of the package of Trader Joe's Ube Mochi Pancake & Waffle Mix to the mixing bowl. Mix until a thick dough forms.

Shape the cookies - Line a baking sheet with parchment paper. In a small bowl, mix 1 1/2 tablespoons of cinnamon with 2 tablespoons of granulated white sugar. Use a cookie scoop or spoon to portion out the dough into 1 1/2-inch (4 cm) balls. Roll each ball in the cinnamon sugar mixture until coated, then place on the lined baking sheet, spacing them about 2 inches (5 cm) apart.

Bake the cookies - Bake the cookies for 10-12 minutes, until the edges are slightly golden but the centers are still soft. Remove from the oven and let cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely.

Serve and store - Serve the cookies warm or at room temperature. Store any leftovers in an airtight container at room temperature for up to 3 days.