Preheat the oven to 350 degrees. Grease and flour a 10-cup Bundt pan. In a medium-sized bowl, mix together the flour, baking soda, baking powder, 1 ½ teaspoon cinnamon and salt. In the bowl of a stand mixer or using a hand mixer, beat the ¾ cups butter and 1 cup sugar and brown sugar until light and fluffy. Slowly incorporate the eggs and egg yolk, one at a time. Add the sour cream and beat until incorporated. Add the vanilla. Turn the mixer to low speed and add the dry ingredients slowly; mix until just combined. Pour the batter into prepared pan and cook for 55 to 60 minutes. Remove from oven and let cool for 20 to 30 minutes before turning out onto rack to cool completely. Melt ½ cup butter in a small saucepan. In a small bowl, mix ¾ cup sugar and 3 teaspoons cinnamon. Brush the cake all over with melted butter, and coat with the cinnamon sugar. Drizzle the chocolate sauce on individual slices and serve.