Heat the oil a deep-fat fryer to 190C. Alternatively, heat the oil in a deep, heavy-based saucepan until a breadcrumb sizzles and turns golden-brown when dropped into it. (Caution: Hot oil can be dangerous. Do not leave unattended.)
Mix the chopped ham and parmesan into the cold risotto, then roll the risotto into small balls, each about the size of a golf ball.
Sprinkle 40g/1½oz of the flour onto a plate. Beat the eggs in a bowl. Sprinkle the breadcrumbs onto a separate plate. Dust each risotto ball in the flour, then dip into the beaten egg, then roll in the breadcrumbs until completely coated.
Carefully lower the arancini into the hot oil in batches and fry for 2-3 minutes, or until golden-brown and heated through. Remove from the pan using a slotted spoon and set aside to drain on kitchen paper. Keep warm.
Meanwhile, in a bowl, whisk together the cornflour, the remaining flour and the sparkling water until smooth and well combined. Dip the courgette flowers into this batter.
Fry the courgette flowers in batches for 1-2 minutes, or until the batter is crisp and golden-brown. Remove from the pan using a slotted spoon and set aside to drain on kitchen paper.
Serve the arancini with the courgette flowers and lemon wedges alongside.