To make the crumbles, preheat the oven to 350°. Line a baking sheet with parchment. 

In a mixer, add both sugars, flour, baking powder, salt, and sprinkles. Mix on low to combine. 

Add oil and vanilla and mix on medium until clumps form, it takes about 2 minutes. Turn out into a bowl and set aside. 

No need to wash the bowl, add butter and sugar and beat on medium until light and fluffy, about 3-4 minutes. 

Add egg and both vanillas, scraping the bowl. 

Add cake flour, flour, cornstarch, baking powder, and salt. Mix until just combined. Add in sprinkles and give one more quick mix until incorporated. 

Use a cookie scoop and portion the dough onto baking sheets, 3-4 inches apart. These cookies spread. Gently press the tops with a glass to flatten and add a generous amount of crumble to the top of the cookies. 

Bake for 10 to 12 minutes. Let cool for a few minutes, then transfer to a wire rack to cool completely.