Line the base of your spring form pan with parchment paper. This is to help you slide the finished cake to a serving platter when done.
Cut the panettone into roughly 1" cubes.
Beat the eggs with the sugar until light and frothy. Beat in the sour cream and then the whipping cream and 9 Tbsps Marsala. Beat until mixture is thick and spreadable. Transfer 1 cup to a separate container and reserve. You will use this to top the cake just before serving.
Rough chop the pistachios, dried cranberries and chocolate chips (not necessary if using mini chocolate chips).
Set aside and reserve 25 grams each of the chocolate chips and pistachos. You will use these to decorate the top of the cake when ready to serve. Add the remaining chocolate chips and pistachios to the remaining cream mixture.
Line the bottom of the spring form pan with ⅓ of the panettone pieces. Sprinkle 2 Tbsps of the Marsala evenly over the bottom layer. Lightly press the panettone together so the cream mixture will soak in not drip through the bottom. Cover with ½ the cream mixture.
Make a second solid layer of panettone pieces, drizzle with 2 Tbsps Marsala and cover with the 2nd half of the cream mixture.
Make a top layer of panettone pieces and sprinkle with the remaining 2 Tbsps Marsala. Smooth the layer out and press lightly. Cover with plastic wrap and refrigerate overnight or up to 2 days.
When you are ready to serve, unmold the spring form pan. Use an offset spatula to gently transfer the cake from the spring form bottom to your serving plate. The parchment paper will come with you so just be aware that you don't cut in to it when you are serving.
Slather the top with the reserved cream mixture. Traditionally the sides are left bare but you can 'ice' the side lightly as well if you have enough cream mixture. Sprinkle the reserved chocolate chips, reserved pistachios and pomegranate arils evenly over the top.
Slice and serve.
The cake should be served within 2 days from the point of assembly. Leftovers will keep another day or so but be aware the cake will get a bit softer and soggier with each passing day.
Leftovers can be frozen in an airtight container up to 3 months. The defrosted cake is very soft so presentation is compromised somewhat but it still tastes delicious.