- Preheat the oven at 170ºC/ 340ºF conventional oven and prepare a 20x20 cm/8x8 in square baking pan with parchment paper. 
- Blend the Biscoff cookies to a sand-like texture. Sift together the all-purpose flour, baking powder, baking soda and salt. Then add the Biscoff cookie crumbs and stir it together. Set it aside. - 30 g Biscoff cookies, 150 g all-purpose flour, ¼ teaspoon baking powder, ¼ teaspoon baking soda, ¼ teaspoon salt 
- In a large bowl using an hand whisk add the oil and granulated sugar and mix it together until combined. Then add the Biscoff spread and mix until combined. - 60 g vegetable oil, 150 g granulated sugar, 40 g Biscoff cookie spread 
- Add the eggs one at a time into the mixture and mix it in until combined. - 2 large eggs 
- Scrape down the sides of the bowl and continue by adding the flour mixture, mixing until just combined. 
- Finally add the sour cream and vanilla extract and mix until just combined, make sure not to over mix the cake batter. - 120 g sour cream, 1 teaspoon vanilla extract 
- Using a rubber spatula, give the batter a gentle fold to make sure all of the ingredients have combined. 
- Pour the cake into the prepared pan and bake for 30-35 minutes or until a cake tester comes out clean. 
- Let the cake cool on a cooling rack. After 10 minutes, gently remove the cake from the cake tin and let the cakes cool down completely.