Add the softened butter to a mixing bowl and beat until creamy.
Add the granulated sugar and brown sugar.
Add the vanilla extract. Add the egg and egg yolk.
Then beat until fully incorporated.
In a separate bowl, whisk together the all-purpose flour, baking soda, baking powder, and salt.
Gradually add the dry ingredients to the wet mixture and mix until a soft cookie dough forms.
Add the white chocolate chips and chocolate chips, then mix until evenly distributed.
Fold in the crushed biscuits and mini marshmallows.
Take a portion of dough, place a marshmallow in the center, and cover it completely with the dough.
Arrange the filled cookie dough portions on a parchment-lined baking sheet, leaving space between each cookie.
Bake at 350°F (175°C) for 10–12 minutes, or until the edges are lightly golden.
Remove the cookies from the oven and allow them to cool completely on a wire rack.
For the glaze, melt the white chocolate with the heavy cream and stir until smooth.
Spread the white chocolate glaze over each cooled cookie.
Add a small piece of chocolate and sprinkle with crushed biscuits.
Allow the glaze to set, then serve and enjoy.
