Very interesting crossword, but 3 we're having difficulty parsing:
3d Kind of film about fungal growth in kind of pastry (?shortcrust)
22d Taunts with it and starts to scoff (d-g- I-) ?digs it
4d All but nullify a monarch that's gigantic and awfully distant (?Quasar) Perhaps 'Quas(h) a R(ex)?