1/2 cup (1 stick) unsalted butter, room temperature
1/2 cup plus 2 tablespoons confectioners' sugar
1 large egg yolk
3 1/2 ounces high-quality milk chocolate (such as Lindt or Perugina), chopped
2 cups heavy whipping cream, divided
1/4 cup (1/2 stick) unsalted butter
1/2 cup plus 2 tablespoons sugar
3 tablespoons water
Unsweetened cocoa powder (for dusting)
Crust: Whisk flour and cocoa in medium bowl.
Beat butter and confectioners' 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 4 1/2-inch
diameter tartlet pan with removable bottom.
Refrigerate crusts for 1 hour or freeze for 30 minutes.
Heat oven to 375 degrees F.
Bake cold crusts until set and dry-looking, about 12 minutes, pressing with back
of spoon if bubbles form. Cool crusts in pans.
Filling: Place milk chocolate in medium bowl. Bring 1 1/2 cups cream to
simmer in small saucepan. Pour hot cream over chocolate; let stand 1 minute, then
whisk until melted and smooth. Cover with plastic wrap and refrigerate until cold,
for at least 4 hours or overnight.
Combine remaining 1/2 cup cream and butter in small saucepan and stir over medium
heat until butter melts; remove from heat.
Combine sugar and 3 tablespoons water
in heavy small saucepan. Stir over medium-low heat 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-butter 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 milk chocolate-cream mixture until peaks form;
spoon atop caramel in crusts, dividing equally (about 1/2 cup for each crust) and
Chill at least 2 hours.
Remove tartlets from pans.
Lightly sift cocoa powder over tartlets and serve.
Makes 6 servings.
Do ahead: Can be made 8 hours ahead. Cover and keep refrigerated.