Line a brownie tin or a small casserole dish with parchment paper so the entire bottom is covered and the parchment paper also covers the sides.
Spread the biscoff spread, evenly, on the parchment paper so the entire bottom is covered. You may also crush up 2-3 biscoff cookies and press them into the spread. Place in the freezer for 1 hour.
When the biscoff has approximately 15 minutes left in the freezer, preheat your oven to 350 degrees F.
Prepare the flax egg by combining + mixing 2 tbsps of ground flax with 5 tbsp of water. Let the mixture sit for 10 minutes. It will appear jelly like once it is done.
Using an electric mixer, cream the room temperature vegan butter. This can take up to 2 minutes. You will need to scrap the sides of your bowl often. You will know the butter is creamed once it appears fluffy and airy.
Add in the brown and granulated sugar, mixing again until it is combined with the butter. The mixter will be slightly gritty.
Add in the flax egg, vanilla, melted dark chocolate chips and oat milk then mix again until combined. It will be slightly looser now.
Combine the flour, baking soda, cocoa powder and salt togther in a medium bowl, then combined it into the batter, mixing until combined (approx. 2 minutes). The batter will be fluffy.
Add in half of the non melted chocolate chips and mix until combined.
Remove the biscoff from the freezer. If you are using a glass dish, please see my tips below. Remove the biscoff from the parchment paper. It should peel off very easily due to the oils. If it does not, freeze it longer. If it breaks apart, its ok! You may discard the parchment paper.
Grease brownie dish + spoon half of the brownie batter into the bottom of the brownie dish, spreading it evenly. You may need to use a greased spoon.
Place the layer frozen biscoff on top of the first layer of brownie mix. If the biscoff broke apart, simply do your best to place it together so it is one layer.
Spoon the rest of the brownie batter on top of the frozen biscoff and spread evenly.
Option to sprinkle 2 extra tbsps of chocolate chips on top of the top layer of the brownie batter. Just be sure to press them into the batter,
Place the lotus biscoff cookies directly on top, pressing them into the batter. I used 7 cookies, breaking on in half.
Bake for 40 minutes. Insert a toothpick into the brownies. If it comes out cleanly, remove the brownies and let cool for 15 minutes. If the toothpick did not come out cleanly, bake for another 5-10 minutes, repeating the insertion of the toothpick every 5 minutes.