Stir together brown sugar, cinnamon and cocoa. Add butter; blend with a fork until the mixture resembles coarse crumbs.
Stir in nuts. Set aside.
Preheat oven to 350°F. Butter a 9-inch square or 10-inch round cake pan.
Cream butter and sugar. Add eggs and beat until light and fluffy.
Combine flour, baking soda, baking powder and salt; add to butter mixture alternating with the sour cream. Mix until blended.
Pour half of the batter into the prepared pan. Sprinkle half of the streusel mixture over the batter. Then sprinkle chopped apricots evenly over the streusel layer.
Pour the remaining batter on top and sprinkle with the remaining streusel mixture. Bake 45 to 50 minutes or until cake test done.