Melt the chocolate in the top of a double boiler over hot water. Smooth with a whisk and remove from heat. (Or melt the chocolate in a microwave for 1 to 1-½ minutes, or until smooth when stirred.) Cream the butter, gradually adding the sugars. Beat in the eggs one at a time, then the vanilla. Fold in the melted chocolate. Sift together the flour, cocoa, baking soda, and salt. Stir into the creamed ingredients. Fold in the nuts and chocolate chips. Cover and refrigerate the dough for 20 minutes. Preheat oven to 350 degrees F. Roll the dough into 1-½-inch balls and place on buttered cookie sheets; leave room between them. Bake for 15 minutes. Cool briefly on sheets, then transfer to a rack and cool.