Preheat your oven to 350°F (177°C). Finely crush the Biscoff cookies using a food processor or a rolling pin.

In a bowl, mix the crushed cookies with melted unsalted butter until combined. Press the mixture into a 9-inch pie dish.

Bake for 10-12 minutes until fragrant, then let it cool completely.

In a medium bowl, whisk the egg yolks until smooth. In a saucepan, combine the granulated sugar and water over medium heat, bringing it to a boil.

Remove from heat and stir in the heavy cream, mixing fully. In another saucepan, whisk together brown sugar, cornstarch, and salt; gradually whisk in whole milk.

Bring the mixture to a boil, then slowly add it to the whipped egg yolks while whisking constantly. Return to heat, cooking for 2-3 minutes until thickened.

Remove from heat and stir in a bit of butter for richness. Pour the filling into the cooled crust and smooth the top.

Cover the pie and refrigerate for at least 6 hours or overnight to set the filling properly.

In a mixing bowl, beat heavy whipping cream, powdered sugar, and vanilla bean paste until soft peaks form.

Spread the whipped cream topping over the butterscotch filling. Garnish with pecans and crushed cookies if desired.

Slice the pie into wedges and serve chilled.