Chlorophyllum molybdites

Anytime -- you're happy, I'm happy. :)

At first glance I'm thinking Chlorophyllum molybdites (sometimes grouped as a Lepiota with green spores, L. molybdites, as suggested by Clive), the green-spored parasol. Thriving within grass, in temperate zone (tropics), the stem being equal or longer than the cap is wide and its classic brown stem at maturity (it looks completely similar to the few C. molybdites I've seen), the ring near the cap which is double-edged, the brown upward-peeling warts that occur more towards the center of a white cap, and the close or fairly close gills all point to this species, to the best of my knowledge. It seems to be young due to the white gills (should eventually turn green or dull gray), but the darkening of the stalk occurs upon maturing, so I'll let you decide. Hands off; it's poisonous (if it is C. molybdites, that is!)! And such a majestic specimen you've found, thanks for sharing! :)