Heat the oil and butter in a heavy saucepan, add the onions and cook until they are translucent.

Add the rice and stir until it is well coated with the butter and oil mixture.

Add the white wine and stir continually over medium heat until it is absorbed.

Start to add 1/2 cup of hot broth and tomato mixture, stirring as it is absorbed.  Continue in this manner, adding ladles full of hot broth, and stirring continuously for about 20-25 minutes or until the rice is cooked, but remains slightly firm to the teeth.  Stir in the grated cheese and basil and season with salt and pepper.

Refrigerate risotto, covered, for 8 hours, or overnight.

Place the flour in one shallow bowl, the eggs and milk in another, and the breadcrumbs in a third bowl.  Take a small handful of the rice and place in your palm creating an indentation in the center. Place a piece of cheese in the center and wrap the rice around the cheese creating an oblong shape.

Continue to use up all the rice in the same manner making more arancini, placing the finished ones on a baking sheet.

Take each rice ball and first roll in flour, then dip into the egg mixture, and finally roll in breadcrumbs.  Return to the baking sheet and continue to coat the remaining rice balls in the same manner.

Heat the oil in a heavy saucepan to 375 degrees F. Fry 3 or 4 rice balls at a time until crisp and golden brown.

Use a slotted spoon to remove from the oil, and place on a tray covered in paper towels in a warm oven.  Continue to fry the remaining rice balls in the same fashion, then serve hot.

Source : http://www.italianfoodforever.com/2012/11/suppli-alla-romana/