Farm Stand Brownies

3 1/2 cups semi-sweet chocolate chips
1 cup butter
1 1/2 tablespoons instant espresso powder
1 tablespoon vanilla
1/2 cup flour, plus
1 tablespoon flour
1 1/2 teaspoons baking powder
1/2 teaspoon salt
1 1/2 cups chopped walnuts
3 eggs
1 cup sugar, plus
2 tablespoons sugar

Heat oven to 350°F.
Line a 13x9 pan with foil and butter the foil.
Place chocolate chips and butter in a saucepan and stir constantly over medium-low until melted and smooth. Add espresso powder and vanilla and stir. Cool 15 minutes.
Whisk flour, baking powder, and salt in a small bowl. Add walnuts and toss to coat.
Whisk eggs and sugar in a large bowl just to blend. Add chocolate mixture and stir to blend. Add flour mixture and stir to just blend. Pour into pan.
Bake until a tester comes out with moist crumbs, about 35 minutes.
Cool completely. Cover and chill for 6 hours. Remove from pan to work surface. Cut into 16 pieces.