Steps
- Preheat the oven to 350°F / 175°C. Line a 9 × 13in / 23 × 33cm baking pan with parchment paper.
- Warm 115g of unsalted butter, 425g of packed brown sugar, and ¾ teaspoon of salt in a saucepan, stirring until the butter melts. Remove from the heat.
- Let cool until warm. Beat in 3 cold large eggs, one at a time, then 2 teaspoons of vanilla extract.
- Mix in 180g of all-purpose flour and 1 teaspoon of baking powder, then 115g of chopped walnuts.
- Spread in the pan. Sprinkle with 55g of chopped walnuts.
- Bake for 30-35 minutes, until a skewer comes out with moist crumbs and no wet batter. Cool completely before slicing.