Unroll the puff pastry on a sheet of baking paper.The filling goes down the middle of the pastry, so cut diagonal strips into the dough until you are 1/3 of the way in across the pastry sheet. Do this on both sides.See the picture of how the pastry should be cut, just below the recipe.
Spread the middle section with pesto and scatter half the mozzarella over it.
Lay the tomato slices and basil leaves on top, sprinkle over the rest of the mozzarella and season with salt and freshly ground pepper.
Fold the ends of the pastry in over the filling, then fold the strips in over the filling, alternating from side to side, – one at a time.See the video above the recipe if you need to.
Brush the top with a beaten egg and sprinkle with sesame seeds and/or a little finely grated parmesan if you like.
Bake the plait in a preheated oven for about 20 minutes at 200°C, conventional oven (top and bottom heat).
Let it rest for about 5 minutes before slicing and serving.Serve it with a crisp green salad, as a side at a barbecue or as part of a tapas spread.