Place the mascarpone cheese in a large bowl and set aside. With an electric mixer, beat the cream and 1/4 cup of the sugar in a medium bowl until soft peaks form. Fold the whipped cream into the mascarpone. Then fold in the chilled Chocolate Zabaglione. Cover and refrigerate.
Whisk the warmed espresso and the remaining 1/4 cup of sugar in another medium bowl until blended. Line a 9 1/4 by 5 by 2 3/4-inch metal loaf pan with plastic wrap, allowing the plastic to extend over the sides. Working with 1 cookie at a time, dip 8 cookies into the espresso, and arrange in a single layer side by side over the bottom of the prepared pan.
Spoon 1/3 of the mascarpone mixture over the cookies to cover. Repeat dipping 8 of the cookies in the espresso and layering the cookies and remaining mascarpone mixture 2 more times. Dip the remaining 8 cookies in the espresso and arrange side by side atop the tiramisu. Press lightly to compact slightly (the last layer will extend above the pan sides). Cover the tiramisu with plastic and refrigerate at least 6 hours.
Unwrap the plastic from atop the tiramisu. Invert the tiramisu onto a platter. Remove the plastic. Sift the cocoa over the tiramisu, and with a vegetable peeler or sharp knife, make dark chocolate shavings and sprinkle over top.