Preheat your oven to 350°F (177°C). Crush 1.5 cups of Biscoff or Speculoos cookies. Mix with 6 tablespoons of melted unsalted butter and press into a 9-inch pie dish. Bake for 10-12 minutes until golden. Let it cool completely.

In a medium saucepan over medium heat, combine 1 cup of granulated sugar with 1/4 cup of water. Stir until the sugar dissolves, then let it boil until amber, about 8-10 minutes. Remove from heat and whisk in 1 cup of heavy cream until smooth.

In another saucepan, whisk together 3/4 cup of brown sugar, 1/4 cup of cornstarch, and 1/4 teaspoon of salt. Gradually add 2 cups of whole milk while whisking. Cook until it thickens, about 5-7 minutes. Stir in the caramel and 1 teaspoon of vanilla.

Beat 3 egg yolks until frothy. Gradually add some hot filling to the yolks, whisking constantly. Pour back into the saucepan and heat again, stirring until thickened, about 2-3 minutes.

Pour the filling into the cooled Biscoff crust, smooth it out, cover with plastic wrap and refrigerate for at least 6 hours to set.

Whip 1 cup of heavy cream with 2 tablespoons of powdered sugar and 1 teaspoon of vanilla until soft peaks form. Spread evenly over the chilled pie.

Garnish with crushed Biscoff cookies or chopped pecans before serving. Enjoy your Butterscotch Pie chilled.