An old family recipe shared on Smitten Kitchen, that’s destined to become an old family recipe for anyone who chooses to make it – enjoy!
1/2 c. (115 g) butter, room temperature AND 1 1/2 c. sugar
3 eggs, separated AND 1 1/2 t. vanilla
3 c. (390 g) flour AND 1 t. baking powder
1 1/2 t. baking soda AND 3/4 t. fine sea salt
2 c. (455 g) sour cream
Filling and Topping – 2 c. semi-sweet chocolate chips AND 1/2 c. sugar AND 1 t. cinnamon
Preheat the oven to 350 and generously butter a 9 x 13 glass cake pan (if you’re using a metal one, then lining it with parchment is recommended). Using your electric mixer, beat together the butter and sugar for a couple of minutes, then beat in the egg yolks and vanilla, scraping down the bowl as needed.
In a separate medium bowl, whisk together the flour, baking powder, baking soda and salt and in yet another separate bowl, beat the egg whites until stiff (I used my hand mixer here).
To the butter/sugar mix, alternately add in the dry mix and the sour cream until both are gone and the batter is well combined and very thick. Gently fold in the egg whites.
In a small bowl, stir together the sugar and cinnamon for the topping and have the chocolate chips ready.
Scoop half of the batter into your prepared pan, smooth the top, then sprinkle on half of the cinnamon sugar mix and half of the chocolate chips. Dollop on the remaining batter, do your best to smooth the top of this as well, then evenly sprinkle on the remaining cinnamon sugar and chocolate chips. Bake for about 45 minutes – this is tough to measure for ‘doneness’ because of the gooey chocolate and crunchy top crust…but you’ll figure it out! Leave the cake to cool in the pan and do your best to not cover it – this is the only way to maintain the crunch.