Preheat the oven to 350 degrees F. Line an 8x8 square baking pan with parchment paper.
Add biscoff cookies to a food processor. Pulse until fine crumbs form, then add melted butter and continue to mix until the texture resembles wet sand. Firmly press the crumbs into the bottom of the prepared pan into a single even layer. Bake for 12 minutes. Allow it to cool for 10 minutes. 30 Biscoff Cookies1/2 cup Salted Butter
Reduce the oven temperature to 325 degrees F.
Add egg yolks to a large bowl. Use an electric hand mixer and beat on high speed for 3 minutes, until the yolks appear lighter in color and frothy. Add in sweetened condensed milk and continue to mix. Once combined, add the key lime juice (or lime juice), heavy cream, vanilla extract, and key lime zest (or lime zest). 4 Egg Yolks2 - 14 oz cans Sweetened Condensed Milk3/4 cup Key Lime Juice1/4 cup Heavy Cream1/2 tsp Vanilla Extract2 tsp Key Lime or Lime Zest
Pour the filling into the slightly cooled baked crust. Bake for 15-20 minutes, until the edges are set and center is just slightly jiggly. Allow the bars to cool to room temperature, than place in the refrigerator to set for at least 4 hours, ideally overnight.
Combine cold heavy cream, sour cream, vanilla extract, and powdered sugar in a large mixing bowl. Whip on medium speed for 1 minutes, then increase the speed to high and whip together until stiff peaks form, about 3-5 minutes. 1 1/4 cups Heavy Cream1/4 cup Sour Cream2/3 cup Powdered Sugar1 tsp Vanilla Extract
Add the whipped cream on top in an even layer. Serve immediately or refrigerate until ready to serve.
Notes
Be sure to firmly pack the crust into the pan. You can use the bottom of a cup.
Don't overbake! Bake until the filling is just set around the edges and slightly jiggly in the center. It should resemble jello