1 1/2 cups flour
1 t baking powder
1/2 t salt
1 1/2 sticks softened butter
1 1/2 cups packed light brown sugar
2 large eggs, lightly beaten
4 t vanilla extract
1 cup white chocolate chips
1. Adjust oven rack to middle position; heat oven to 350 degrees.
2. Cut 18" length foil and fit foil into length of 13 x 9 " baking pan, pushinig it into corners and up sides of pan; allow excess to overhang pan edges. Spray foil-lined pan with nonstick cooking spray.
3. Whisk flour, baking powder, and salt together in medium bowl; set aside.
4. Whisk softened butter and brown sugar together in medium bowl until combined. Add eggs and vanilla and mix well. Using rubber spatula, fold dry ingredients into egg mixture until just combined; do not overmix. Fold in chocolate and turn batter into prepared pan, smoothing top with rubber spatula.
5. Bake until top is shiny, cracked, and light golden brown, 22 to 25 min; do not overbake. Cool on wire rack to room temperature. Remove bars from pan by lifting foil overhang and tranfer to cutting board. Cut into 2" squares and serve.