¾ cup plus 2 tablespoons all purpose flour
2 tablespoons plus 2 teaspoons unsweetened cocoa powder
½ cup (1 stick) unsalted margarine, room temperature
½ cup plus 2 tablespoons powdered sugar
1 large egg yolk
3½ ounces high-quality chocolate, chopped
2 cups pareve whipping cream, divided
¼ cup (½ stick) unsalted margarine
½ cup plus 2 tablespoons sugar
3 tablespoons water
Unsweetened cocoa powder (for dusting)
Whisk flour and cocoa in medium bowl. Beat margarine and powdered sugar in another medium bowl until well blended. Beat in yolk. Add flour mixture in 2 additions, beating just until blended. Gather dough into ball; flatten into disk. Wrap in plastic and refrigerate 2 hours.
Divide dough into 6 equal pieces. Press each onto bottom and up sides of 4½ inch diameter tartlet pans with removable bottom or use one large tart pan with removable bottom. Refrigerate crusts 1 hour or freeze 30 minutes.
Preheat oven to 375°F. Bake cold crust until set and dry-looking, about 12 minutes, pressing with back of spoon if bubbles form. Cool crusts in pans.
Place chocolate in medium bowl. Bring 1½ cups pareve cream to simmer in small saucepan. Pour pareve hot cream over chocolate; let stand 1 minute, then whisk until melted and smooth. Cover with plastic wrap and refrigerate until cold, at least 4 hours overnight.
Combine remaining ½ cup pareve cream and margarine in small saucepan and stir over medium heat until margarine melts; remove from heat. Combine sugar and 3 tablespoons water in heavy small saucepan. Stir over medium-low hear until sugar dissolves. Increase heat and boil without stirring until color is deep amber, occasionally brushing down sides of pan with wet pastry brush and swirling pan, about 8 minutes. Immediately add hot cream-margarine mixture (mixture will bubble vigorously). Remove from heat and stir until any caramel bits dissolve. Transfer caramel to small bowl and chill until slightly firm (semi-soft), stirring often, about 40 minutes.
Spoon caramel into center of baked crusts (about 2 generous tablespoons for each crust). Set aside.
Using electric mixer, beat chilled chocolate-pareve cream mixture until peaks form; spoon atop caramel in crusts, dividing equally (about 1/2 cup for each crust) and spreading evenly. Chill at least 2 hours. DO AHEAD: Can be made 8 hours ahead. Cover and keep refrigerated.
Remove tartlets from pans. Top with some extra whipped cream and lightly sift cocoa powder over tartlets and serve.