Tip the chickpea flour into a large bowl and make a well in the centre. Slowly whisk in 440ml room temperature water until you have a smooth, lump-free batter. Cover and leave to rest at room temperature for at least 4 hrs, or overnight.

Heat the oven to 240C/220C fan/gas 9 with a large cast iron or ovenproof frying pan on the middle shelf. (Or, use a 30 x 25cm rectangular baking tin.) Meanwhile, uncover the batter and skim any impurities off the surface. Stir, then add the chopped rosemary, 1 tsp fine salt and 1 tsp freshly ground black pepper. Transfer the mixture to a jug.

Carefully remove the hot pan from the oven and pour in the olive oil (do this carefully in case it spits). Put a wooden spoon in the oil and hold it at a 45-degree angle in the centre of the pan. Slowly pour the batter into the pan over the back of the spoon – you are aiming for a farinata with a thickness of about 1cm. Bake for 15 mins on the lowest shelf of the oven until lightly browned. Heat the grill to high, then slide under the hot grill for 5 mins until the top is light golden brown. Cut into wedges, sprinkle with sea salt flakes and serve hot.