Brown Butter Walnut Chocolate Zucchini Bread

Steps

1. Heat the oven to 325°F (165°C). Grease a 9x5-inch loaf pan with the canola oil and line it with a parchment sling.
2. Spread the chopped walnuts on a baking sheet and toast in the oven for 8 to 10 minutes until fragrant; cool, then set aside one quarter of the walnuts for the top and keep the remaining three quarters for the batter. Raise the oven to 350°F (175°C).
3. Grate the zucchini, then squeeze it lightly in a towel to remove some liquid, keeping it moist.
4. Melt the butter in a small pan over medium heat, swirling, until it smells nutty and has brown flecks, 4 to 6 minutes. Pour the brown butter into a large bowl and cool 10 minutes.
5. In a medium bowl, whisk the all-purpose flour, whole wheat flour, baking soda, baking powder, salt, cinnamon and nutmeg to make the dry mixture.
6. Whisk the brown sugar into the brown butter, then whisk in the egg, sour cream and vanilla until smooth. Stir in the zucchini.
7. Fold the dry mixture into the wet mixture until just a few streaks remain, then fold in the reserved three quarters of the walnuts and all of the chocolate chips.
8. Scrape the batter into the pan. Toss the remaining quarter of the walnuts with the granulated sugar and scatter this walnut-sugar topping over the batter.
9. Bake 60 to 65 minutes, tenting with foil after 40 minutes if the top browns fast, until a toothpick in the center comes out clean of wet batter (melted chocolate is fine).
10. Cool in the pan 15 minutes, lift out and cool on a rack at least 1 hour before cutting into 12 slices.