- Sift the flour into the mixing bowl. Add the butter and rub in until the mixture resembles fine breadcrumbs. Stir in the sugar.
- Lightly beat the egg yolk with 1 tbsp cold water. Add the flour mixture and mix in with a round-bladed knife. Gather together to make a soft dough.
- Wrap in cling film and chill for at least 30 minutes before rolling out.
- Roll out and line with 12 individual tartlet cases and blind bake for about 15-20 minutes.
- Next, prepare the filling. Melt the chocolate and butter together, either over a pan of simmering water or in the microwave on medium power. Allow to cool slightly.
- Beat the eggs and add in the sugar a little at a time, then add the chocolate mixture and mix until everything is well combined. Sift in the flour and stir well.
- Tap the tin to get rid of any excess air. Sift in the flour and stir well. Spoon into pastry cases and bake for around 20 minutes, until the brownies are cooked but not firm.
- Cover with marshmallows and brown with either a blow torch or under a grill.