For the batter, mix the flour and cornflour with 200ml ice cold water. Unlike most batters, you don’t want it to be too smooth and little pockets of flour are good as they will go really crispy. Take each courgette flower and trim away any excess stem. Then stuff each flower with a slice of mozzarella and an anchovy. Gently dip into the batter, holding onto the stem. Heat the oil to 180°C (if a cube of bread browns in 15-20 seconds, the oil is hot enough). Taking care of the hot oil, deep-fry the courgette flowers in batches for 2-3 minutes until crisp and a light golden brown. Remove from the oil, drain on kitchen paper and serve.