This is quite straight forward you simply need to defeat the boss on Veggie Village (world 2) you need 30 clover leaves to unlock the door.
Make sure you pick up the extra life on the right hand lily pad on the right hand side before you go on the platform (it can't be collected after you start the boss battle).
Stage 1 stand to the side of the platform to avoid her charge forward stand a little backward from the front and wait for the switch platform to raise (4 in total 2 down each side near the corners) hit each switch you should be able to hit them all before any of the attacks are launched. Lazer's down the middle and fireballs each side, you will have to jump the first 2-3 fireballs while you wait for the charge to shoot her,
Stage 2 Kill the 4 bees, once they are done stand to the side again and wait for her to charge forward again, there is now a foot stamp attack which could be either left or right side of the platform so stand in the middle. Eight switch platforms will now raise up 2 at the back, 2 down each side and 2 at the front. The boss attack this time has two row's of Lazer's moving vertically up and down and horizontally across the platform. It isn't possible to do all of the switches before the Lazer's start up so just double jump them and work your way around the screen.
Stage 3 Same as Stage 2 except there are 2 foot stamps at the end (mine always cam from the same side) just stay in the middle. There are only six switch platforms this time none at the front of the platform. Again start hitting them as soon as they appear this time the boss attack is a rotating fireball attack. Just jump the fireballs hit all the switches which starts the final boss hit.
Congratulations you've got the achievement.
I've made a video if you would prefer to watch that