How to Make It
Heat oven to 350° F. Spread the pecans on a rimmed baking sheet and toast, tossing once, until fragrant, 6 to 8 minutes. Let cool, then roughly chop. In a medium bowl, whisk together the flour, cocoa powder, and salt.
Using an electric mixer, beat the butter and sugar on medium-high until creamy, 2 to 3 minutes. Beat in the egg yolks. Reduce mixer speed to low and gradually add the flour mixture; mix until combined but still crumbly.
Press the dough into the bottom and up the sides of a 4-by-14-inch rectangular (or 9-inch round) tart pan. Line with a large piece of parchment paper, leaving an overhang on all sides, and fill with dried beans or pie weights. Place the pan on a rimmed baking sheet and bake until the edges of the crust are dry, 20 to 22 minutes. Remove the parchment and beans and bake until dry and set, 10 to 12 minutes. Let cool completely.
Meanwhile, in a large bowl, combine the chocolate and pinch of salt. In a small saucepan, bring the cream to a bare simmer; pour over the chocolate and let stand 1 minute. Stir gently until the mixture is smooth. Stir in 1½ cups of the pecans. Pour the mixture into the cooled tart shell and sprinkle with the remaining pecans. Refrigerate until set, at least 1 hour.