Preheat the oven to 190C/ and line a baking tray with greaseproof paper.

Place the butter and sugar into a bowl and beat on medium until pale and fluffy, approximately 3 minutes with an electric mixer.

Add the egg and continue to beat until well combined, beating for a further minute.

Toss in the crushed biscuits, flour, baking powder and baking soda and combine until no dry portions remain in your bowl.

Add the chocolate chunks and marshmallows and stir until combined and strewn through your cookie dough.

Scoop a piece of dough and roll the the top of your cookie dough into the remaining ⅓ of chocolate chunks, flattening slightly as you place it on the tray.

Continue scooping and rolling into the chocolate pieces, pressing lightly when you place onto the tray, ensuring there is 1 ½ inches between each cookie.

Bake for 12 minutes or until golden at the edges.

Allow to sit on your baking tray for 3 minutes before placing on a cooling rack

Serve with a glass of milk.

Enjoy!