Preheat oven to 325 degrees F. Line an 8-inch square baking pan with parchment or foil, allowing for an overhang on all four sides. Set aside.
Cookie Crust: In a food processor, pulse together Speculoos Cookies, graham crackers, and salt until mixture resembles even coarse sand. Transfer to a medium bowl. Add melted butter and mix until combined. Press mixture into the bottom of the prepared baking pan to form the crust. Set aside.
Cookie Butter Cheesecake Swirl: Using an electric mixer, beat cream cheese until smooth. Add sour cream and mix until incorporated. Scrape down bowl as needed to ensure thorough mixing. Add sugar. Mix on low speed until mixture is smooth.
Add eggs one a time on low speed. Add vanilla and salt. Continue to mix on low speed until mixture is smooth. Pour cheesecake batter over cookie crust. Use a mini offset spatula to level cheesecake.
Place cookie butter in a microwave safe bowl. Microwave for 10-15 seconds until cookie butter is fluid. Be careful not to burn cookie butter in the microwave. Drizzle fluid cookie butter over cheesecake batter. Using a knife or a chopstick, swirl together cheesecake batter and cookie butter.
Bake for 45-50 minutes until the center of the cheesecake no longer jiggles and the edges of the cheesecake has slightly pulled away from the pan. Cheesecake may puff slightly in the oven, but will flatten once cooled.
Let cheesecake cool to room temperature in pan. Transfer to fridge and let chill for at least 1 hour, overnight is best. Once cheesecake is chilled throughout, remove from pan by lifting the parchment overhang. Slice cheesecake into bite-sized squares.*