Make the icing hands: Line 3 baking sheets with parchment paper. Beat the meringue powder and water in a large bowl with a mixer on medium speed until medium glossy peaks form, 3 to 4 minutes. Beat in the vanilla. Gradually beat in the confectioners' sugar until the icing is thick and stiff peaks form; add more water, 1/2 teaspoon at a time, if the icing is too thick to pipe. Transfer to a pastry bag fitted with a 1/8-inch round tip.
Pipe hands (2 1/2 inches tall and 1 1/2 inches wide) onto the prepared baking sheets. (Do not press the pastry tip against the baking sheet -- the hands might break.) Pipe and fill a 1-inch triangle "anchor," pointed-side down, at the bottom of each hand. Pipe knuckles onto each finger. Reserve the remaining icing in a resealable container to fix any broken bones. Let the hands dry overnight.
Make the pudding: Whisk the milk, granulated sugar, cocoa powder, cornstarch and salt in a large saucepan until smooth. Cook over medium heat, whisking occasionally, until thickened slightly, about 15 minutes.
Whisk the egg yolks in a medium bowl. Gradually whisk about 1/2 cup of the warm milk mixture into the egg yolks, then pour the mixture into the saucepan. Continue to cook over medium heat, whisking, until thickened, about 9 minutes. Remove from the heat and whisk in the chocolate until melted and smooth. Whisk in the butter and vanilla. Divide the pudding among 12 small bowls. Place a piece of plastic wrap directly on the surface of each and refrigerate until set, at least 2 hours or overnight.
Loosen the hands from the parchment with an offset spatula. Use the reserved icing to repair any broken bones. Gently press the hands into the pudding cups and sprinkle with crushed cookies.