Chocolate Tartlets with Butter-Orange Cookie Crust

FOR THE CRUST:
Preheat oven to 350 degrees F. Blend all ingredients in a food processor just until dough forms. Transfer dough to work surface. Gather dough into ball. Cut dough into 8 equal pieces. Press 1 dough piece over bottom and up sides of each of eight 4 3/4 inch tartlet pans with 3/4-inch-high sides and removable bottoms, forming 1/4-inch-thick crusts. Pierce crusts with fork. Refrigerate until firm. Bake until crusts are pale golden, about 18 minutes. Cool in pans on rack.

FOR THE FILLING:
Stir chocolate and butter in large wide metal bowl set over saucepan of simmering water until melted and smooth. Remove from heat. Cool 10 minutes, stirring occasionally.

Using electric stand mixer and whisk attachment, beat sugar, eggs, yolks, Grand Marnier, orange peel and salt in large bowl until very thick ribbon falls when whisk attachment is lifted, about 8 minutes. Sift flour over egg mixture, then fold in. Fold egg mixture into cooled chocolate mixture. Transfer batter to prepared crusts, dividing equally.

DO-AHEAD TIP:
Can be made 1 week ahead. Freeze 1 hour. Cover and keep frozen.

Arrange tartlets on baking sheet. Bake until filling puffs and begins to crack, about 15 minutes for room temperature tartlets and 25 minutes for frozen tartlets. Place tartlets on plates and serve.