Preheat oven to 325-degrees. Line a 9x13 pan with aluminum foil and grease surface.
For the Biscoff swirl: In a small bowl, combine the cookie butter spread, cream cheese, sugar, and egg, until smooth. Set aside.
For the brownies: Sift together the cocoa, salt and baking powder and set aside.
In a medium saucepan, melt the butter over low heat. Remove from heat and add the sugar. Once they are mixed, return to the burner and keep stirring as it heats through. You don't want it to bubble.
Remove the pan from heat and stir in the cocoa mixture. Let it cool a few minutes. Whisk in the eggs and vanilla extract until smooth. Stir in the flour. Pour into the prepared pan and smooth it out.
Dollop the Biscoff mixture here and there on top of the brownie batter. Use a table knife to gently swirl the mixture every which way across the surface.
Bake for 30-35 minutes, until the swirl looks set and it passes the toothpick test. Cool on a wire rack before cutting.