1-Getting Started: First, preheat your oven to 350°F (175°C) and position the rack in the center. Lightly spray a 9-inch square baking pan with non-stick spray or line it with parchment paper to ensure easy removal later. This step sets the stage for your chocolate chip blondies recipe for high altitude, helping achieve that golden brown finish.

2-Mixing and Baking: Melt the 1 cup unsalted butter and let it cool for 10 minutes to avoid cooking the eggs prematurely.

3-Mixing and Baking: Whisk the melted butter with 2/3 cup granulated sugar, 2/3 cup light brown sugar, 1 tablespoon vanilla extract, and 2 large eggs for 2 minutes until smooth and light in color.

4-Mixing and Baking: In a separate bowl, mix 2 1/2 cups all-purpose flour (fluffed, spooned, and leveled), 1 1/4 teaspoons baking powder, and 3/4 teaspoon coarse kosher salt.

5-Mixing and Baking: Stir the dry ingredients into the wet mixture using a spatula until fully combined, then let the dough cool for 5 minutes if it’s warm.

6-Mixing and Baking: Fold in 1 cup semi sweet chocolate chips and 1/2 cup chopped pecans if using, then spread the dough evenly into the prepared pan.

7-Mixing and Baking: Bake for 35 minutes until puffed and golden brown, or 30 minutes for a gooier center adjust for high altitude to prevent drying out.

8-Mixing and Baking: Cool completely for 4-6 hours before cutting into 16 squares; for advance prep, cool several hours, cover with plastic wrap, and let it sit overnight.