Grate chocolate finely in a grater. Cut the Bauducco Chocolate Panettone into slices and set aside. Combine coffee and rum and sprinkle Bauducco Chocolate Panettone slices with this liquid. Prepare a cream by mixing milk, sugar, and lemon juice and mascarpone cheese. In a baking dish, assemble the tiramisu making layers in this order: cream, grated chocolate, slices of moistened Bauducco Chocolate Panettone; repeat another layer and finish with a layer of cream and grated chocolate. Put in refrigerator for an hour and serve cold.