Heat oven to fan assisted 170C / 190C / 375F / gas 5.
Measure couscous into a heatproof bowl, pour in the hot water, mix well and let stand for 10 mins.
Stir in egg, herbs, Parmesan and salt until well combined.
Transfer couscous pizza dough unto a lined baking tray, spread out and shape into a pizza using the back of a spoon.
Bake pizza dough for about 15 mins until set and a little crispy on the edges.
Remove pizza base from the oven and scatter on the mozzarella, and then the sardines, tomatoes and olives and bake for a further 7 mins.
Remove the pizza from the oven and top with rocket and shredded sorrel leaves before eating.