Place unpopped popcorn kernels in a paper lunch bag. Fold top over twice and microwave for 2½ minutes. Pour in to a large bowl, removing unpopped kernels, and set aside.
In a metal bowl set over simmering water, melt white chocolate, stirring until smooth. Add cookie butter and stir until combined.
Pour hot cookie butter mixture over popcorn in bowl, sprinkle with sea salt to taste, and stir quickly but carefully to coat.
Spread wet popcorn on a baking sheet, and sprinkle crushed cookies and sprinkles liberally. Allow to dry for at least an hour.
Cookie Butter Cupcakes
Preheat oven to 350 degrees F. Line 2 standard cupcake pans with ~18 liners.
In a medium bowl, whisk together flour, baking powder, and salt. Set aside.
In the bowl of a stand mixer fitted with a paddle attachment, cream butter and brown sugar on medium speed for 2 minutes, until fluffy.
Add vanilla, then eggs, one at a time, mixing until combined.
Alternate mixing in flour and buttermilk, beginning and ending with flour mixture, until just combined. Don't overmix.
Fill liners ⅔ full of batter. Bake 20-25 minutes, until toothpick inserted in the center comes out clean.
Cool in cupcake pans for 10 minutes, then remove to cooling rack. Cool completely before icing.
Frost each cupcake with chocolate buttercream using a butter knife or spatula, creating slightly domed sides, with a flat top. Top with cooled cookie butter popcorn, or just garnish with more sprinkles.