Preheat oven to 180ºC . For cake, cream butter and sugar in a large bowl until fluffy. Add eggs, beating until smooth. In a medium bowl, sift together flour, baking powder, and salt. Gradually add dry ingredients to creamed mixture, blending well. Gently fold in sour cream and vanilla. For topping, combine all ingredients in a small bowl. For glaze, melt butter and chocolate chips ina small saucepan over low heat,s tirring until smooth. Sprinkle 2 T. topping in bottom of greased and floured 23 cm tube pan. Spoon half of cake batter into pan. Sprinkle 4 T. topping over batter and drizzle half cup glaze over topping. Spoon remaining batter into pan and sprinkle with remaining topping. Reserve remaining glaze. Bake 1 hour to 1 hour 15 minutes or until a toothpick inserted in center comes out clean. Cool 10 minutes in pan. Turn onto serving plate. Drizzle remaining glaze over top of warm cake. ----