Preheat oven to 325°F. Prepare mega mini fluted tube pan with vegetable pan spray.
In small bowl, combine flour, baking powder, baking soda and salt.
In large bowl, beat butter and sugar with electric mixer until light and fluffy. Add eggs, one at a time, scraping down sides of bowl. Add vanilla and beat well. Add flour mixture in two additions alternately with sour cream, mixing until just combined.
For streusel, stir together brown sugar, cinnamon and flour in small bowl. Cut in butter until mixture resembles coarse crumbs. Divide half of streusel evenly among the cavities. Pipe or spoon half of the cake batter evenly among cavities. Sprinkle remaining streusel over and top with remaining batter.
Bake 20-22 minutes or until toothpick inserted in center comes out clean. Cool in pan on cooling grid 5 minutes; remove from pan and cool completely on grid.
For topping, combine brown sugar and butter in small sauce pan. Melt butter and add corn syrup. Stir over medium heat until smooth and sugar has dissolved. Remove from heat and cool slightly. Pipe or pour over cakes.