Preheat oven to 350°F. Lightly grease a 13- x 9-inch pan. Line bottom and sides with parchment paper, allowing 2 to 3 inches to extend over sides; lightly grease parchment paper.

Prepare the crust: Pulse chocolate wafers in a food processor until finely ground. Stir in melted butter and sugar. Press evenly into bottom of prepared pan.

Prepare the batter: Combine chocolate chips and butter in a medium saucepan. Cook over medium, stirring often, until melted, about 4 minutes. Remove from heat; cool 1 minute.

Whisk in sugar. Add eggs, 1 at a time, whisking until well blended after each addition. Whisk in flour, vanilla, and salt. Fold in pecans. Pour into prepared pan; smooth top.

Bake in preheated oven until a wooden pick inserted in the center comes out with moist crumbs, about 30 minutes. Cool completely in pan on a wire rack, about 1 hour. Lift brownies from pan, using parchment paper sides as handles. Cut into 24 squares.