For Sauce: Puree berries in processor. Strain through sieve, pressing on solids with back of spoon. Mix in juice and cassis. Refridgerate. (Can be prepared 2 days ahead.)

For Brownies: Preheat oven to 350. Butter 9 inch square baking pan. Stir butter and unsweetened chocolate in heavy medium saucepan over low heat until melted. Remove from heat. Mix in sugar, vanilla, and salt. Add eggs, one at a time, mixing after each addition. Mix in flour. Stir in nuts and chips. Pour batter into prepared pan. Bake until tester insterted into center comes out with moist crumbs still attached and to feels firm to touch, about 35 minutes. Cool. Cut into squares. Serve with sauce.