Preheat the oven to 180°C (350°F). Grease and line a 23–25 cm (9–10 inch) round cake pan.
Make the sponge: In a large bowl whisk the Eggs with the Granulated Sugar until very pale, thick and ribbon-like (8–12 minutes by hand or 4–6 minutes with a mixer). Gently fold in the sifted 00 Flour and a pinch of Salt until just combined, keeping as much air in the batter as possible. Pour into the prepared pan and bake 22–30 minutes, or until a skewer comes out clean. Cool completely on a wire rack.
Slice the cooled sponge horizontally into 2–3 even layers. Reserve the top layer for the top of the cake or to cut into decorative shapes.
Prepare the soaking syrup: In a small saucepan combine Water and the remaining granulated sugar and bring to a simmer until the sugar dissolves; cool slightly and stir in the Alchermes Liqueur to taste (start with 3–4 tablespoons).
Brush each sponge layer lightly with the liqueur syrup to moisten and flavor the cake.
Make the ricotta filling: Drain any excess whey from the Sheep's Ricotta by pressing it through a sieve or using a cheesecloth for 30–60 minutes. Whip the drained ricotta smooth with Powdered Sugar and a little Lemon Juice until creamy and sweetened to your taste.
Fold into the ricotta mixture the chopped Dark Chocolate and the chopped Mixed Candied Citrus Peel so the filling is studded with fruit and chocolate.
Assemble the cake: Place one soaked sponge layer on your serving plate, spread a thick layer of ricotta filling, then repeat with remaining layers. Reserve some filling to cover the sides and top for a thin crumb coat. Chill the assembled cake for 30–60 minutes to firm up.
Roll and color the marzipan: Knead the Marzipan (Almond Paste) with a few drops of Green Food Coloring until evenly tinted, adding a little extra Powdered Sugar if the paste is too soft. Roll the marzipan to a circle large enough to cover the chilled cake.
Cover the chilled cake with the rolled marzipan, smoothing it down and trimming the excess. Use remaining ricotta or a little powdered sugar to help seal any edges if needed.
Decorate the top with Assorted Candied Fruit, extra pieces of candied peel and chocolate shards, arranging them in an attractive pattern. Dust lightly with Powdered Sugar if desired.
Chill the finished cassata for at least 4 hours or preferably overnight to allow the flavors to meld before slicing and serving. Keep refrigerated and serve at cool, not icy, temperature.
