In a large bowl, stir together the flour, sugars, salt and cinnamon.
Melt the butter and allow to cool just slightly so it's still melted but not hot.
Stir the butter into the dry ingredients and do not break up clumps unless they are huge. Set aside.
For the Cake
Heat the oven to 350 degrees and spray a 9x13" pan with nonstick spray and set aside.
In a standing mixer, beat the butter and sugar until fluffy, about 1-2 minutes. Add the oil and mix again.
Crack in your eggs and add the vanilla and then give the mixer a final turn before dumping in all dry ingredients. Mix until almost incorporated and then add in the buttermilk and stir until barely combined.
Spread 1/3 the batter evenly in the pan and sprinkle generously with 1/3 of the streusel.
Spread another layer of batter and then another 1/3 of the streusel. Repeat one final time, ending with the streusel on top.
Bake 50-60 minutes, tenting with foil after 40-45 minutes if it's browning too quickly, or until a toothpick in the center comes out clean.
Allow to cool slightly then drizzle with the icing and serve warm. (see note)
For the Icing
In a bowl, whisk together the powdered sugar, vanilla and heavy cream until a steady ribbon of drizzle comes off the whisk. Set aside.
Altitude really matters here so your cake could be done at 40-50 minutes while ours is usually closer to 50-60.
This cake is awesome to make ahead! Even two days prior to your event is fine if you cover it well.
Better than Starbucks Coffee Cake
Amount Per Serving (1 slice)
Calories 645Calories from Fat 243
% Daily Value*
Saturated Fat 18g113%
Trans Fat 1g
Polyunsaturated Fat 1g
Monounsaturated Fat 6g
Vitamin A 631IU13%
Vitamin C 1mg1%
* Percent Daily Values are based on a 2000 calorie diet.