Load up world 1-2 in single player. The clock in this kitchen does not start until after you serve the first meal. So just toss rice into each of the three pots, dump them out and toss rice into them again, and again until the achievement pops.
Tracking does not work during the stage (just in case you thought you could check your progress during it), but the achievement does pop once you complete the 100 hot-pot-shots.
Edit: Some commenters had some confusion, so I should add that you have to toss/throw (with X) the items into the pot, not just place/put the items in the pot.