• Preheat oven to 350F and spray 13x9 baking pan with non-stick cooking spray.

Streusel Topping

• Melt butter in a medium-sized bowl in 10 second increments stirring in between each interval until just melted.  Allow to cool a bit if butter is too hot. 
• Use a fork to whisk together  the flour, sugars, cinnamon, and salt. Pour in  melted butter to mixture and use a fork to stir until combined and has crumble texture.  

Cinnamon Swirl

• In another small bowl, whisk together brown sugar and cinnamon for cinnamon swirl. Set aside.

Cake

• In separate, medium-sized bowl, whisk together flour, baking powder, cornstarch and salt. Set aside.
• Using a mixer, in a large bowl, cream together butter and softened cream cheese.
• Add in sugars and beat until light and fluffy.
• Add eggs, one at a time, beating until combined.
• Stir in vanilla extract.
• Add flour mixture to wet mixture, alternating with some of the buttermilk several times mixing with each addition until all combined.
• Spread almost half of the thick batter into prepared pan.
• Sprinkle the CINNAMON SUGAR mixture evenly over the batter.
• Spoon remaining batter over the cinnamon sugar layer and use a knife to spread evenly over the top. You can also swirl the batter to get more cinnamon swirls, optional.
• Sprinkle STREUSEL TOPPING evenly over batter.
• Bake on 350F for 40-50 minutes. Check doneness with a toothpick.
• Allow to cool before cutting and serving.

Glaze (optional)

• If desired, make glaze by whisking together powdered sugar and milk together to get the consistency desired.
• Drizzle over cooled coffee cake.