Melt chocolate chips with butter. Mix in brown sugar and let cool. Add eggs, mix in vanilla, baking powder and salt. Add flour and finely chopped walnuts. Mix well.

Chill dough for at least 4 hours, overnight is even better.

When you're ready to bake, preheat oven to 350 degrees, with rack in the middle position. Roll walnut-sized dough balls with your hands. (Messy - I wear thin plastic gloves). If dough becomes too sticky, return to the refrigerator to chill while cookies are baking.

In a small bowl, coat dough balls with white sugar. Place on a greased cookie sheet and flatten with a greased spatula. Bake at 350 degrees for 12-14 minutes. Let cool on cookie sheet for one minute, then remove to wire racks.