1. Heat oven to 350°F. Line 48 small muffin cups (1-3/4 inches in diameter) with paper or foil baking cups.
2. Beat butter, sugar, water and vanilla in large bowl on medium speed of mixer until well blended. Add eggs; beat well.
3. Stir together flour, cocoa, salt and baking soda. Gradually add to sugar mixture, beating on low speed just until blended. Stir in 1/2 cup nuts. (If necessary, refrigerate dough until firm enough to handle.) Shape dough into 1-inch balls; place in prepared muffin cups.
4. Bake 11 to 13 minutes or until cookie surface is set. Cookies will appear soft and moist. Do not overbake. Cool about 5 minutes on wire rack. Press 3 to 4 chocolates into surface of each cookie cup. Cool completely in pan on wire rack.
5. Place remaining chocolates in heavy-duty resealable plastic food storage bag. Microwave at MEDIUM (50%) 30 seconds; knead bag and chocolates. If necessary, microwave at MEDIUM an additional 15 seconds at a time, kneading after each heating, until chocolates are melted. Cool slightly. Cut off corner of bag about 1/8 inch from point. Lightly drizzle tops of cookie cups. Before drizzle sets, lightly sprinkle tops with remaining nut pieces. Makes 48 cookies.