Toast hazelnuts on rimmed baking sheet in 350°F oven until fragrant, about 8 minutes. Place in clean towel; rub briskly to remove as much of the skins as possible. Let cool; chop coarsely. In bowl, beat egg yolks with sugar until pale and thickened, Add ricotta; beat until smooth. Stir in hazelnuts, chocolate, orange rind and vanilla. Scrape into tart shell and smooth top.
On lightly floured surface, roll out reserved pastry. Using fluted pastry wheel or knife, cut into ¾ -inch wide strips, rerolling scraps. Brush pastry rim with water. Weave strips over filling, ½ inch apart, to make lattice top, pressing ends firmly to rim. Trim pastry at rim. Whisk remaining egg yolk with 1 tbsp water. Brush over lattice.
Bake in bottom third of 425°F oven for 15 minutes. Reduce heat to 350°F; bake until filling is firm, about 30 minutes. Let cool on rack. (Make-ahead: Cover and refrigerate for up to 8 hours. Let stand at room temperature for 30 minutes before serving.)
In large bowl, sift together flour, cocoa, sugar and salt. Using pastry blender or 2 knives, cut in butter and shortening until mixture resembles fine crumbs with a few larger pieces.
In liquid measure, whisk together 1 of the egg yolks and vinegar. Add enough ice water to make 1/3 cup. Drizzle over flour mixture; using fork, briskly stir until dough holds together. Gather dough and press into disc. Wrap in plastic wrap and refrigerate until chilled, about 30 minutes. (Make-ahead: Refrigerate for up to 3 days.)
On lightly floured surface, roll out three-quarters of the pastry to 1/8-inch thickness. Fit into 9-inch tart pan with removable bottom. Trim off excess and press together with remaining pastry. Press into disc; wrap in plastic wrap and refrigerate until chilled, about 30 minutes.