Preheat oven to 220°C. Place the cauliflower in a food processor. Process until very finely chopped. Transfer to a frying pan. Place over medium-high heat. Cook, stirring, for 2-3 mins or until the cauliflower is heated through. Set aside for 5 mins to cool slightly.
Place cauliflower in a clean tea towel. Squeeze the cauliflower in the tea towel to remove excess liquid. Transfer the cauliflower to a large bowl. Add egg and parmesan and stir to combine. Season.
Line a large baking tray with baking paper. Spoon the cauliflower mixture onto the lined tray. Use a palette knife or the back of a metal spoon to spread and press the cauliflower into a 25cm-diameter disc. Bake for 15 mins or until golden brown.
Meanwhile, place the mint, garlic, hazelnuts, extra parmesan and 100g of the rocket in a clean food processor and process until finely chopped. With the motor running, gradually add the oil in a thin, steady stream until well combined. Season.
Transfer the pizza base to a serving platter. Spread the base with half the pesto. Top with bocconcini, prosciutto and remaining rocket. Drizzle with the remaining pesto to serve.