Preheat the oven to 350°F (180°C) and spray a 9x13 baking dish with non-stick spray and line it with parchment paper so that there is overhang on either side.
Sift all purpose flour and cocoa powder into a mixing bowl and add salt. Mix together.
Add butter and ½ cup of chocolate chips to a microwave safe bowl and microwave in 30-second intervals, bringing it out to stir every 30-seconds, until melted.
Add white granulated sugar, eggs and vanilla extract to the melted butter and chocolate and whisk everything together.
Now add the wet ingredients in with the dry and mix into a thick brownie batter.
Add chopped biscoff cookies and chocolate chips and fold into the batter.
Transfer the batter to your prepared 9x13 baking dish and smooth down.
Add biscoff cookie butter to a microwave safe bowl and microwave in 15-second intervals, bringing it out to stir every 15-seconds until melted. Use a teaspoon to drizzle this over the top of the brownies.
Place into the oven and bake for 30 minutes until the top is dry and shiny on top.
Let them cool for 30 minutes before using the parchment paper overhang to lift them out of the dish and place them onto a wooden board.
Let them cool completely before cutting into squares and serving.