Mix the flour, semolina and salt in a bowl. Add the yeast, water and oil, mix with a risotto spoon. Knead into a soft, smooth dough using the dough hook on a food processor for approx. 10 mins. Cover and leave to rise at room temperature for approx. 1½ hrs. until doubled in size.
Sprinkle a little semolina over the work surface, roll out the dough into a rectangle (approx. 30 x 40 cm), place on a baking tray lined with baking paper. Spread the parmesan and mozzarella on top of the dough. Mix the squash and mushrooms with the oil and salt. Squeeze the sausage meat out of the skin and cut into pieces approx. 2 cm long. Arrange the sausage, squash and mushrooms on top of the cheese.
Approx. 30 mins. on the bottom shelf of an oven preheated to 240°C. Remove from the oven, garnish with the parsley, season.