Preheat the oven to 180˚C/160˚C fan/gas mark 4. Butter a 20cm square tin and line with parchment paper.
Combine the flour, finely crushed biscuits, baking powder and salt in a small bowl.
In a separate mixing bowl, beat the butter and sugar for two minutes until fluffy.
Add the vanilla and eggs and beat for another minute until combined.
Gradually beat in the flour mixture until a dough forms. Transfer the dough to the baking tin and press down into an even layer.
Sprinkle over the chopped chocolate, then top with the marshmallows.
Bake for 20-25 minutes until the marshmallows are browned and the dough has cooked through.
Remove from the oven and press down on each marshmallow, return to the oven for a further minute until the surface is very toasted.
Preheat the oven to 180˚C/160˚C fan/gas mark 4. Butter a 20cm square tin and line with parchment paper.
Combine the flour, finely crushed biscuits, baking powder and salt in a small bowl.
In a separate mixing bowl, beat the butter and sugar for two minutes until fluffy.
Add the vanilla and eggs and beat for another minute until combined.
Gradually beat in the flour mixture until a dough forms. Transfer the dough to the baking tin and press down into an even layer.
Sprinkle over the chopped chocolate, then top with the marshmallows.
Bake for 20-25 minutes until the marshmallows are browned and the dough has cooked through.
Remove from the oven and press down on each marshmallow, return to the oven for a further minute until the surface is very toasted.
