Special equipment: 8-inch square dish
Combine the coffee and 1 cup Frangelico in a pitcher, and allow to cool if the coffee is hot.
Whisk the egg whites till frothy. In a separate bowl beat the yolks and sugar with the 1/4 cup Frangelico for the filling. Add the mascarpone to the yolks and sugar mixture, beating it in well to mix. Gently fold in the foamy egg whites, and mix again.
Pour half of the coffee and Frangelico mixture into a wide shallow bowl and dunk enough Savoiardi cookies for a layer, about 4 at a time, into the liquid, coating both sides. Line your tiramisu dish with the soaked Savoiardi cookies; they should be damp but not falling to pieces (though it wouldn't matter if they did). Pour any leftover liquid from the dipping process over the layer you have made.
Put half the mascarpone mixture on top of the soaked cookies and spread to make an even layer. Pour the remaining coffee and Frangelico mixture from the pitcher into the shallow dish and make another, final, layer of Savoiardi, dipping as before and layering on top of the mascarpone in the dish.
Pour any leftover liquid over the Savoiardi layer, and then cover with the final layer of mascarpone. Cover the dish with plastic wrap and leave overnight, or for at least 6 hours, in the refrigerator.
When you are ready to serve, take the tiramisu out of the refrigerator and remove the plastic wrap. Mix the chopped roasted hazelnuts with 2 teaspoons of cocoa and sprinkle over the top layer of mascarpone. Then dust with the final teaspoon of cocoa powder, pushing it through a strainer for lighter coverage, over the nut-rubbly tiramisu.
The tiramisu can be made 1 to 2 days ahead and stored in refrigerator. It will keep for up to 4 days in total and leftovers should be refrigerated immediately. Freeze Note: The tiramisu can be frozen for up to 3 months. Wrap the tiramisu (without hazelnut and cocoa topping) in double layer of plastic wrap and layer of aluminum foil. Thaw overnight in refrigerator and top with nuts and cocoa, as directed in recipe.
Consumption of raw or undercooked eggs, shellfish and meat may increase the risk of foodborne illness.
From NIGELLA KITCHEN by Nigella Lawson. Copyright 2010 Nigella Lawson. Published by Hyperion. Available wherever books are sold. All Rights Reserved.