Preheat your oven to 350°F (175°C). Line a baking sheet with parchment paper.

In a large mixing bowl, cream together the butter and cookie butter with brown and granulated sugars until light and fluffy.

Beat in the egg and vanilla extract until smooth.

In a separate bowl, whisk together flour, cornstarch, baking soda, and salt. Gradually fold into the wet mixture.

Scoop portions of cookie dough onto the baking sheet, spacing them about 2 inches apart.

Bake for 10-12 minutes until the edges are set but the centers remain soft.

Allow cookies to cool on the baking sheet for about 5 minutes, then transfer to a wire rack.

Drizzle extra cookie butter over warm cookies before serving.