Sicilian Rice Balls (Arancini)

Name: Sicilian Rice Balls (Arancini)
Prep time: 1 h
Cook time: 3 h 5 min
Total time: 4 h 5 min
Cuisine: European, Italian, Mediterranean
Ingredients: 1200 g water; 1 tsp fine sea salt; 400 g risotto rice (e.g. Arborio, carnaroli); 25 g unsalted butter, diced; 80 g Parmesan cheese, grated (see tip); 1 medium egg; 1 pinch saffron powder; 40 g onion, quartered; 30 g olive oil; 100 g beef mince, broken in pieces; 200 g tinned chopped tomatoes; 30 g fresh mushrooms, sliced; 1 Tbsp tomato purée; ½ tsp fine sea salt; 1 pinch ground black pepper; 70 g frozen green peas; 2 medium eggs, beaten; 300 g mozzarella, drained, cut in 18 pieces; 100 - 150 g breadcrumbs; oil (e.g. sunflower, vegetable), for frying