Preheat your oven to 350°F (175°C) and grease your cake pans. Line the bottoms with parchment paper for easy removal.

In a medium bowl, whisk together flour, cornstarch, baking powder, baking soda, cinnamon, and salt until evenly combined.

In a large bowl, beat butter, oil, granulated sugar, and brown sugar until light and fluffy, about 2–3 minutes.

Add eggs one at a time, mixing well after each addition to create a smooth batter.

Stir in vanilla extract and cookie butter until fully incorporated.

Add half of the dry ingredients into the wet mixture and gently mix.

Pour in the buttermilk and mix until just combined.

Add the remaining dry ingredients and fold carefully to avoid overmixing.

Divide the batter evenly between prepared cake pans and smooth the tops.

Tap pans lightly on the counter to remove air bubbles.

Bake for 30–35 minutes or until a toothpick inserted in the center comes out clean.

Remove cakes from oven and let them cool in pans for 15–20 minutes.

Transfer cakes to a wire rack and cool completely before frosting.

For the frosting, beat butter until creamy and smooth.

Gradually add powdered sugar, mixing on low speed until combined.

Add milk, vanilla, and cookie butter, then beat on medium-high until fluffy.

Level cake layers if needed using a serrated knife.

Place the first layer on a cake stand and spread frosting evenly.

Add a drizzle of cookie butter and sprinkle crushed cookies.

Place the next layer on top and repeat the process.

Frost the entire cake, smoothing the sides and top.

Drizzle melted cookie butter over the top for a drip effect.

Decorate with extra frosting swirls or cookie crumbs if desired.