Preheat the oven to 375 degrees F. Butter a 9-by-5-inch standard loaf pan.
Make the cinnamon sugar: In a small bowl, mix together the sugar and cinnamon
Make the batter: In a large bowl, using an electric mixer at medium speed, beat the eggs until frothy, about 3 minutes. Add the sugar and vanilla, beating until smooth. In a medium bowl, whisk together the flour, baking powder, baking soda, and salt.
Add the melted butter and sour cream to the egg-and-sugar mixture; beat until well combined. At low speed, add the dry mixture to the wet mixture a spoonful at a time, beating just until smooth. Fold in the chocolate chips.
Spread half of the batter in the prepared pan and sprinkle evenly with about two-thirds of the cinnamon sugar. Sprinkle with the walnuts. Top with the remaining batter, spreading evenly, then sprinkle with the remaining cinnamon sugar.
Bake for 50 to 55 minutes or until a knife or skewer inserted in the center comes out clean.
"How to Celebrate Everything: Recipes and Rituals for Birthdays, Holidays, Family Dinners and Every Day in Between" by Jenny Rosenstrach © Ballantine Books 2016. Provided courtesy of Jenny Rosenstrach. All rights reserved.