Preheat the oven to 180C/ 350F and line an 8-inch springform with parchment paper.
In a mixing bowl, combine granulated sugar , butter, and brown sugar until it forms a creamy mixture. Then mix in the egg and vanilla extract.
¾ cups light brown sugar, 1 egg, ¾ cup butter, ¼ cup granulated sugar, 1 teaspoon vanilla extract
After that add the biscuit crumbs, flour, and baking soda, mix.
1 cup biscuit crumbs, 1.25 cups all-purpose flour, ½ teaspoon baking soda
Add the milk and mix again. Stir in the chocolate chips then pour the batter in the springform.
1 cup chocolate chips, 2 tablespoon milk
Bake for 40 minutes then take the springform out of the oven and sprinkle the marshmallows on top of it. Put it back in the oven and broil for 10 minutes.
2 cups marshmallows
Notes
The secret to a soft and fluffy cookie cake is baking until just light brown on the edges. So,don't overmix.