Combine brown sugar and flour; cut in butter until mixture resembles coarse crumbs. Stir in walnuts and chocolate pieces.
1 c. mini semi-sweet chocolate pieces Combine softened cream cheese, granulated sugar and butter. Mix until well blended on medium speed of electric mixer; blend in eggs and vanilla. Combine dry ingredients; add alternately with milk, mixing well after each addition. Stir in chocolate chips. pour into greased and floured 33 cm x 23 cm baking pan. Sprinkle with crumb topping. Bake in preheated 180ºC oven for 50 minutes or until wooden pick inserted into center comes out clean. Cool. Store in refrigerator.
Note: The original recipe called for only 8 oz. cream cheese, if memory serves. This makes at little creamier coffeecake. I like it better this way, but that's just MHO. For fat watchers, use fat-free cream cheese if you don't mind sacrificing some flavor.