Method
1. Pre-heat oven - 175°C / 350°F
2. Grease a 9x9-inch baking pan
3. Sift all purpose flour into a clean medium bowl
4. Add salt, baking powder, baking soda and walnuts to the dry ingredients. Mix well and set aside
5. Stir the brown sugar into the melted butter and mix well. Cool slightly
6. Mix the beaten egg and vanilla into the brown sugar mixture
7. Add flour mixture, a little at a time, mixing just until combined
8. Spread the batter into the prepared pan
9. Sprinkle chocolate chips on top
10. Bake in the preheated oven until a toothpick inserted in the center comes out clean, about 20 to 25 minutes