Chocolate Chip Sour Cream Coffee Cake

Heat oven to 350°F (175°C). Butter a 9-x-13-inch baking pan and line the bottom with parchment paper.

In a large bowl, cream butter and 1 1/2 cups granulated sugar. Beat in egg yolks and vanilla.

Whisk flour, baking soda, baking powder, and salt together into a separate bowl.

Alternately mix in sour cream and then dry ingredients into butter mixture until both are used up and the batter is smooth and very thick.

In a medium bowl with clean beaters, beat egg whites until stiff, then fold gently into batter.

In a small dish, combine the cinnamon and remaining 1/2 cup granulated sugar for filling and topping.

Spread half the cake batter in the bottom of prepared pan and spread smooth.

Sprinkle with half of the cinnamon-sugar mixture and 1 cup of chocolate chips.

Dollop remaining cake batter over filling in spoonfuls. Use a rubber or offset spatula to gently spread it over the filling and smooth the top.

Sprinkle batter with remaining cinnamon-sugar and remaining chocolate chips.

Bake for 40 to 50 minutes, rotating halfway through, until a tester inserted into the center of the cake comes out clean.

Let cool in pan.