To a double boiler add the egg yolks, granulated sugar, and Grand Marnier. Whisk together and cook over a double boiler until a pale yellow color and creamy consistency. Place over a bowl of cold water to cool.
To a bowl, add the heavy cream, start beating on a medium speed until it starts to thicken, and then add in the mascarpone. Continue to beat until a stiff whipped cream forms. Then gently fold in the cooled zabaglione and pistachio spread to the whipped cream mixture. Then fold in the orange zest. Be careful not to deflate the air in the whipped cream.
To the cold espresso, add 1 tablespoon of Grande Monnier. Mix well.
To a 9 inch loaf pan, place a layer of panettone, sprinkle the espresso over the sponge, making sure to cover all of it, but not adding too much to make it soupy.
Then take half the whipped cream mixture and spread it out over the sponge. Sprinkle with chopped pistachios. Repeat with another layer of panettone, sprinkle with espresso and then add the other half of the whipped cream mixture on top. Smooth it out and sprinkle with more chopped pistachios. As a final touch, add some more orange zest on top.
Cover with plastic wrap and refrigerate overnight so that the tiramisù can set and the flavors can marry.