Preheat the oven to 350˚F. Line an 8×8 inch pan with parchment paper. Set aside.
Melt the butter in a large saucepan over medium heat. Remove from heat.
Mix in the sugar, eggs and vanilla until fully combined. Add in the cocoa powder, flour and salt until just combined. Pour the mixture into the prepared pan.
Melt the biscoff spread in a small saucepan until just melted, stiring constantly. Be careful not to burn it.
Spoon the melted biscoff on the brownies and using a knife, swirl the melted biscoff into the brownie mixture.
Bake in the preheated oven for 25 minutes.