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.