Preheat the oven to 180°C (350°F). Lightly grease a 9x9 inches (23x23cm) square pan with vegan butter (or coconut oil). Then line the pan with a strip of parchment paper.
In a small saucepan, melt vegan butter. Then add brown sugar and white sugar. Whisk until the sugar slightly melt (don’t let it boil). Take it off the heat.
Pour the sugar-butter mixture into a mixing bowl and slowly whisk in applesauce. Then sift all-purpose flour, cornstarch, baking powder, and a pinch of sea salt. Mix until combined. Don't overmix the batter. Mix in chunks of Biscoff biscuits and chopped white nougat chocolate.
Pour the batter into the prepared baking pan and spread it evenly. Add additional nougat chocolate and Biscoff biscuits on top. Bake in preheated oven for 18 minutes. Blondies are done when a toothpick inserted in the middle comes out with a few moist crumbs. If it looks too wet, bake for additional 5 minutes.
Remove blondies from the oven and place them on a cooling rack. Let them cool completely in the pan before cutting into squares.
Drizzle them with melted Biscoff spread and serve.