Preheat the oven to 210°C.
Prepare the sauce by heating the olive oil in a saucepan over a moderate heat. Add the passata, sugar and seasoning. Bring to a simmer and cook for 4-5 minutes until thickened. Remove from the heat and leave to one side.
Combine the flour, salt, yeast and sugar in a large mixing bowl. Mix in the oil and water to form a dough, bringing it together with your hands, then kneading gently on a lightly floured surface for a minute until even. Roll out to the desired thickness, roughly 30cm in diameter.
Spread the tomato sauce on top and sprinkle the grated mozzarella on top. Top with the sliced mushroom, black olives and chopped ham. Arrange on a baking tray and bake for 18-22 minutes until golden and risen.
Remove from the oven and sprinkle the pizza with the dried oregano. Garnish with sprigs of basil before serving.