To make the streusel, combine brown sugar, cinnamon in a bowl and mix. Add in the butter in small pieces and using a pastry cutter, mix until you get small crumbs. Can be done with knives if you don’t have a pastry cutter. Add in the chocolate chips and pecans and stir. Place the bowl in the refrigerator until ready to assemble.
Preheat the oven to 350 degrees.
To make the cake, cream the butter and sugar together until light and fluffy. Add in the eggs, one at a time until well mixed. Mix in the milk and vanilla.
In a small bowl, whisk together the flour, salt, baking powder and baking soda.
Starting with the flour, add in about ¼ of the total amount to the butter/sugar mixture and stir. Add in about ⅓ of the sour cream and mix. Alternate until both flour and sour cream are incorporated.
Grease a 13” x 9” x 2” pan. Add in about half of the cake mixture, spreading an even layer on the bottom. Add a layer of streusel on top, and then drop big spoonfuls of the cake batter over the top and gently spread it out, taking care not to mix in the streusel. Add the remaining streusel layer on top and place in the oven and bake for 30 minutes. Cover with a piece of foil and continue to bake for another 30-35 minutes, until a toothpick comes out cleanly.
Let the cake cool for about 20 minutes before adding the glaze.
To make the glaze, whisk together powdered sugar, milk and vanilla in a small bowl and drizzle over the top of the slightly cooled cake. Slice and enjoy!