Prepare the Cake:

1. Preheat your oven to 350°F. Grease and flour a 9×13-inch baking pan.
2. In a medium bowl, whisk together the flour, baking powder, and salt.
3. In a large bowl, beat the egg yolks with ¾ cup of sugar on high speed until the yolks are pale yellow. Stir in the milk and vanilla.
4. Pour the egg yolk mixture into the flour mixture and gently mix until combined.
5. In a separate bowl, beat the egg whites on high speed until soft peaks form. Gradually add the remaining ¼ cup of sugar, beating until stiff peaks form.
6. Gently fold the egg whites into the batter, being careful not to deflate them.
7. Pour the batter into the prepared baking pan and spread it evenly.
8. Bake for 25-30 minutes or until a toothpick inserted into the center comes out clean. Allow the cake to cool completely.

Make the Milk Mixture:

1. In a medium saucepan, combine the sweetened condensed milk, evaporated milk, whole milk, and Biscoff spread.
2. Heat over low to medium heat, stirring constantly, until the Biscoff spread is fully melted and incorporated. Do not bring to a boil.
3. Remove from heat and let the mixture cool slightly.

Soak the Cake:

1. Once the cake is cool, use a fork or skewer to poke holes all over the top.
2. Slowly pour the milk mixture over the cake, making sure to get it into all the holes.
3. Cover the cake with plastic wrap and refrigerate for at least 4 hours, or preferably overnight, to allow the cake to soak up the milk mixture.

Make the Whipped Topping:

1. In a large bowl, beat the heavy cream with powdered sugar and vanilla extract until soft peaks form.
2. Add the Biscoff spread and continue beating until stiff peaks form.

Assemble the Cake:

1. Spread the Biscoff whipped cream evenly over the top of the soaked cake.
2. Garnish with crushed Biscoff cookies and drizzle with additional melted Biscoff spread if desired.

Serve:

1. Slice and serve the cake chilled. Enjoy the creamy, spiced flavors of your Biscoff Tres Leches Cake!