Sift together the flour, bicarbonate of soda and salt. Cream the butter and both sugars until soft. Lightly mix the egg and vanilla essence and gradually beat into the creamed mixture. Stir in the sifted flour and beat well. Finally stir in the chocolate chips and the walnuts.
Spoon heaped teaspoonfuls of the mixture on to greased baking trays. Space the cookies a little apart to allow