In a microwave-safe bowl, combine the milk chocolate chips and coconut oil. Heat in the microwave in 30-second increments, stirring in between, until completely melted and smooth.
Using a spoon, pour a small amount of the melted chocolate mixture into the bottom of each silicone muffin cup or mini muffin tin. Use the back of the spoon to gently spread the chocolate up the sides, creating a cup shape. Make sure to leave room for the filling.
Place the chocolate-filled muffin cups in the refrigerator for about 15-20 minutes, or until the chocolate is firm.
In a mixing bowl, beat together the butter and cookie butter until smooth. Gradually add the powdered sugar and graham cracker crumbs, mixing until well combined and creamy.
Once the chocolate cups have set, remove them from the refrigerator. Spoon the cookie butter filling into each chocolate cup, filling them to the top.
Reheat any remaining melted chocolate mixture if necessary. Pour a spoonful of the melted chocolate over each filled cup, ensuring the filling is completely covered.
Return the filled and topped cups to the refrigerator for another 20-30 minutes, allowing the chocolate to set completely.
Once set, carefully remove the Chocolate Cookie Butter Cups from the silicone cups or muffin tin. Serve chilled or at room temperature, and enjoy the delightful combination of chocolate and cookie butter!