Crisp Cocoa-Pecan Cookies

Whisk flour, cocoa, baking soda, and 1/2 teaspoon (generous) salt in medium bowl. Stir butter and next 5 ingredients in another medium bowl until smooth. Stir in flour mixture, then nuts. Cover and chill until firm enough to scoop, at least 4 hours. DO AHEAD: Can be made 1 day ahead. Keep chilled. Position 1 rack in top third and 1 rack in bottom third of oven; preheat to 325 °F. Line 3 large baking sheets with parchment. Measure 2 level tablespoonfuls dough; roll between palms into ball. Place on prepared sheet. Using fingers, spread out dough to 3-inch-diameter disk. Repeat with remaining dough, spacing 5 inches apart. Bake cookies 8 minutes; reverse sheets. Bake cookies until flat and beginning to darken around edges, about 10 minutes. Transfer cookies on parchment to rack (cookies will crisp as they cool). DO AHEAD: Can be made 4 days ahead. Store airtight at room temperature. Place rack inside rimmed baking sheet. Place chocolate chips in small microwave- safe bowl. Heat chips in microwave in 15-second intervals until smooth, stirring occasionally. Place cookies on rack. Drizzle melted chocolate over cookies. Let stand until chocolate sets, about 30 minutes.