Preheat the oven to 350 degrees F. Grease and flour a 9x13 inch pan In a large mixing bowl, beat the butter and sugar with an electric mixer for about 4 minutes. Add eggs one egg at a time, as well as vanilla and sour cream/Greek yogurt. In a separate bowl: Sift flour, baking powder, baking soda and salt. Add the flour into the butter and sugar mixture.  Stir together with a mixer on low speed until well combined.

To make the streusel topping:  In a medium-sized bowl combine flour, sugar, cinnamon and butter.  Stir to blend.   Spread the flour mixture into a pan then sprinkle with streusel mixture. Bake in the oven for about 30-45 minutes or until a toothpick inserted into the center of the cake comes out clean.

*Optional: I like to serve my coffee cake with chocolate ganache and use chocolate ganache to garnish the cake. Simply pour chocolate ganache over the top of the cake.

To make chocolate ganache:  Heat cream in a small saucepan, then simmer. Remove from heat and whisk in chocolate.