Add the sweetened condensed milk and 1/2 cup of the Biscoff cookie butter to a large bowl. Whisk until smooth and combined, set aside.
Place the remaining Biscoff cookie butter in a microwave-safe bowl. Microwave for 30 seconds or until slightly melted. Set aside.
In a large bowl, beat the heavy whipping cream and vanilla extract with an electric mixer, until stiff peaks form. Fold this whipped cream into the sweetened condensed milk/cookie butter mixture until just combined. Gently fold in 1 cup of chopped Biscoff cookies.
Using a 9x5-inch loaf pan, pour 1/3 of the ice cream mixture into the pan. Spread out evenly. Add a couple drops of the melted cookie butter over the top. Top with another 1/3 of the ice cream, spreading out evenly. Add a few more drops of melted cookie butter over that ice cream and repeat with remaining ice cream and melted cookie butter.
Using a knife, gently swirl the drops of cookie butter into the ice cream. Sprinkle the very top with the remaining 1/4 cup chopped cookies. Cover the pan with a lid or with plastic wrap. Place in the freezer for at least 8 hours. Serve and enjoy!