Prepare: Preheat the oven to 350 degrees Fahrenheit (180 degrees Celsius). Lightly grease the baking pan and line it with parchment paper, leaving an overhang so that you can easily lift the blondies once cool.
Batter: Melt the butter in a small saucepan or place it in a stirring bowl and melt it in the microwave. Add brown sugar and vanilla extract. Whisk well. Whisk in the egg. Add flour and salt, and combine. Stir in the chocolate chips and chopped walnuts with a spoon.1 stick unsalted butter/ 115 g + 1 cup brown sugar/ 200 g + 1 teaspoon pure vanilla extract + 1 large egg + 1 ¼ cup all-purpose flour/ 160 g + ¼ teaspoon fine sea salt + ½ cup chocolate chips/ 120 g + ½ cup chopped walnuts/ 60 g
Bake: Transfer the batter to the prepared tin. Bake for 20-25 minutes (I needed exactly 22 minutes) or until lightly brown around the edges but still slightly undercooked in the middle (Note 6). Let cool in the pan.
Cut into squares before serving.
Notes
Measurements: It’s preferable to use a kitchen scale when baking; it ensures the best results. Using too much flour will result in a cakey, tough blondie. If using cups, spoon the flour into the cup and level it with a knife.
Preferably unsalted butter with at least 80% fat. Don’t use reduced-fat butter, spread, or margarine for making blondies or brownies.
Sugar: Light or dark brown sugar.
Chocolate: Milk or semisweet chocolate chips or chopped chocolate. For a change, use white chocolate chips.
Or other nuts you like (pecans, macadamia, hazelnuts, almonds).