Whisk together the flour, cocoa powder, and salt. Set aside.

Using an electric mixer on medium speed, beat the butter and sugar until light and fluffy. Add the egg yolks and mix well.

Reduce mixer speed to low. Gradually add the flour mixture, mixing just until combined but still a bit crumbly.

Press the crust mixture into the bottom and up the sides of a 4"x 14" rectangular tart pan or a 9-inch round tart pan with a removable bottom.

Line the crust with parchment paper so that the paper overhangs on all sides. Fill the pan with pie weights (or dried beans). Place the pan on a rimmed baking sheet.

Bake 20 to 22 minutes, or until the edges of the crust are dry. Then, carefully remove the parchment paper and pie weights. Continue baking the crust for 10 to 12 minutes, or until dry and set.

Cool the crust completely.

Allow the pecans to cool. Then, chop them roughly. Set aside 1/4 cup of the pecans for garnish.

Combine the chocolate and a pinch of salt in a large bowl.

Place the cream in a small saucepan. Bring to a simmer. Remove the pan from the heat and pour the cream over the chocolate. Allow to sit for 1 minute. Then, stir gently until the mixture is smooth.

Stir in 1 & 1/2 cups of the pecans and the liqueur.

Pour the filling into the cooled tart shell. Sprinkle with the reserved pecans.

Refrigerate for 1 hour, or until set. The tart may be loosely covered and refrigerated for up to 2 days before serving.