Preheat the oven to 325°F.
Crush 20 biscoff cookies and mix with melted butter.
Press crust mixture into a parchment lined 8x8 pan and bake 8-10 minutes.
Let the crust cool.
Beat cream cheese and sugar until smooth.
Mix in cookie butter, sour cream, and vanilla until combined.
Add the eggs and mix on low speed or with a whisk until just combined.
Spread this filling over the cooled crust.
Bake for 30-40 min, until edges are set and the center still has a little jiggle.
Cool for at least 30 minutes at room temp, then chill for at least 3 hours or overnight.
Spread a layer of cookie butter over the top of the chilled bars and sprinkle crushed biscoff cookies on top.
Chill again briefly if the top needs to firm up more.
