1. Preheat the oven to 180ºC .
2. Beat the butter and both sugars in a large mixing bowl until light and fluffy. Add the egg and vanilla extract and mix well.
3. Mix the flour, salt, and baking soda in another bowl. Add the dry ingredients to the batter and mix until well blended. Stir in the chocolate chips and walnuts.
4. Drop the dough by small scoops 2 to 8 cm apart on an ungreased cookie sheet. Flatten each scoop with the back of a spoon to about 8 cm in diameter.
5. Bake until the centers are still slightly soft to the touch, 11 to 14 minutes. Let cool on the cookie sheet for 5 minutes, then transfer to racks to cool completely. Makes dozen to 15 cookies