Clementine Darling Tart with Chivalrous Chocolate Crust

Ingredients

• 1 fully baked 9-inch chocolate tart shell (recipe follows)
• 1 cup sugar
• Finely grated zest of 4-5 clementines
• 4 large eggs
• 1/4 cup fresh lemon juice (from 1-2 lemons)
• 1/4 cup of fresh clementine juice (from 2-3 clementines)
• 2 sticks plus 5 tablespoons (10-1/2 ounces)
• unsalted butter, cut into tablespoon-size
• pieces, at room temperature
• 1 1/4 cups all-purpose flour
• 1/4 cup unsweetened cocoa powder
• 1/4 cup confectioners' sugar
• 1/4 teaspoon salt
• 9 tablespoons very cold (or frozen) unsalted butter, cut into pieces
• 1 large egg yolk