Mix the flour and salt in a bowl. Mix together the egg, oil and water, add to the flour. On a lightly floured surface, knead into a smooth dough. Shape into a ball and leave to rest at room temperature for approx. 30 mins. underneath a bowl rinsed in hot water.
Heat the oil with the herbs and garlic in a wide-bottomed pan, cover and set aside 3/4 of the oil with the herb sprigs. In the same pan, sauté the vegetables in batches in the remaining herb oil for approx. 5 mins., season and leave to cool. On a lightly floured surface, roll out the pastry as thinly as possible into a rectangle and place on a cloth. With floured hands, carefully stretch the dough from the middle outwards until it is entirely translucent. Brush the dough with the herb oil, sprinkle with the nuts. Spread the filling over the bottom half of the dough, leaving approx. 2 cm free on either side. Roll up the strudel, place it seam-side down on a baking tray lined with baking paper, brush with herb oil.
Bake for approx. 20 mins. in the centre of an oven preheated to 230°C. Brush the strudel with the rest of the herb oil while baking.