Sprinkle the meat with salt and pepper and let it covered at room temperature until you make the stuffing.
Add the chestnuts and plums, stir for 30 seconds and then add the wine. Cook until the wine evaporates, discard the bay leaf, and set aside to cool.
Make a row of 5 strips of prosciutto on the baking paper making sure that they overlap a little. Make another row with the other 5 strips below the first one making sure that there are no gaps between the prosciutto strips.
Transfer the stuffing in the middle of the rectangle and with the help of the baking paper roll the meat into a roulade.
Without removing the baking paper, wrap with the kitchen twine to secure it. Transfer to a deep baking pan.
Bake for about 40 minutes (15 minutes per pound) or until a thermometer inserted in the meat (not in the center!) registers 165°F (74°C).
Remove the roulade from the oven and continue baking the potatoes until done (about 20 more minutes).
Add the jam, stir to combine, and then add the butter one tablespoon at a time. Remove from heat, taste and add salt and pepper if needed. Transfer to a small bowl or saucer and serve with the roulade.