Preheat your oven to 350°F (177°C). In a food processor, finely crush about 24 Biscoff cookies until they resemble sand. Combine cookie crumbs with melted unsalted butter in a bowl and press into a 9-inch pie dish. Bake for 10-12 minutes until fragrant and slightly firm. Allow to cool completely on a wire rack.

In a medium saucepan, whisk together egg yolks and set aside. In another saucepan, combine granulated sugar and water; bring to a boil over medium heat. Once amber, stir in heavy cream carefully. In a separate pot, whisk together brown sugar, cornstarch, and salt before incorporating whole milk and heating until boiling.

Gently whisk a ladle of hot pudding into the reserved egg yolks to temper them. Combine back into the saucepan with remaining pudding. Cook over medium heat, stirring continuously for 2-3 minutes until thickened. Remove from heat and stir in vanilla bean paste and butter until melted.

Pour the filling into the cooled crust evenly. Cover with plastic wrap touching the filling to prevent skin formation. Refrigerate for at least 6 hours or overnight to set.

Whip the heavy cream with powdered sugar and vanilla until soft peaks form. Spread over the cooled pudding layer. Sprinkle crushed Biscoff cookies and chopped pecans before serving.