Preheat oven to 350°F. Grease 9" quiche pan. CRUST: Mix flour and salt. Gradually add oil and water while beating. Transfer to floured surface, place parchment on top, and roll with pin. Fold into two, floured-side in, and repeat a few times -- this ensure dough comes out flaky. Transfer rolled circle of dough to pan, pierce with fork, layer with tin foil, and pour in pie weights. Bake 15min. FILLING: Fry onions and mushrooms in butter. Remove partially baked crust from oven and change oven temperature to 400°F. Lay the prepared fillings into the pie crust (onion, mushroom, ham, tomato). Whisk eggs, ricotta, parmesan, salt, nutmeg, and milk. Pour into crust. Lower heat to 350F and bake 40 min until golden brown and toothpick comes out clean.