Mix flour, salt, yeast, milk, and eggs in a food mixer until smooth.
Add butter gradually piece by piece while mixing for five minutes.
Place dough in an oiled 1 litre container and let rise until doubled.
Roll dough on a floured surface into a 40-50cm rectangle about 1.5cm thick.
Layer prosciutto, broken mozzarella pieces, and chopped basil over the dough.
Roll the dough tightly from the long side and cut lengthwise to expose filling.
Twist the two strips together and form into a circular crown shape.
Place on a lined tray inside a plastic bag to rise for 1.5 hours.
Preheat the oven to 200°C.
Brush with beaten egg and salt, then sprinkle with grated parmesan.
Bake for 25 minutes until golden-brown and leave to cool slightly.