Crush biscoff biscuits with a rolling pin or a food processor and combine the crumbs with melted butter.
Pour into the 8 inch or 20 cm springform pan. Press down the crust mixture on the bottom and the sides of the springform pan with a hand then flatten using glass and place it into the fridge.
Preheat oven to 325ºF or 160°C.
In a big bowl, beat cream cheese using a hand mixer or stand mixer on a medium-low speed until smooth, soft and creamy, about 2 minutes.
Add ¼ of the granulated sugar, and beat until well combined. Repeat the step to the rest of the granulated sugar.
Add the eggs one at a time at a low speed, beating after each addition until well combined.
Once the eggs have been added, scrape the side and the bottom of the bowl with a spatula. Add vanilla extract.
Add cornstarch and flour, beat until well combined. Do not over mix.
Add sour cream and biscoff spread to the cheesecake mixture and beat well. Scrape the side and the bottom of the bowl with a spatula again and make sure all the ingredients are well combined.
Pour the cheesecake batter into a springform. To ensure it does not leak, wrap springform using aluminum foil.
Bake the cheesecake for 45 minutes. When baking, do not open the door of the oven. The cheesecake is done when a small area in the center should be slightly jiggly and the edges should be puffed and light golden brown.
After 45 minutes, turn off the oven and let the cheesecake sit in the oven for 1 hour after that let it completely cool at room temperature.
Refrigerated the cheesecake for at least 6 hours or overnight.
In a saucepan, heat the biscoff spread and heavy cream over medium-low heat, stir until there is no lump.
Turn off the heat then transfer the sauce to a bowl and let it cool completely.
Spread the biscoff sauce on top of the cheesecake using an offset spatula.
For neat slices, wipe the knife until clean and dip into warm water for every slice.
Biscoff cheesecakes are ready to serve. Enjoy!