Easy achievement, you'll need two pieces of Wheat and any two Cows.
Wheat is collected by growing seeds, you get seeds by punching out grass. Take the grass, create a hoe and then use the hoe on any ground though near water is best for results. Place the seeds on the same spot you just used the hoe on. They will grow over time, note that using Bonemeal which is a grinded bone from skeletons can make it grow faster. It's done once it's a brownish green color.
Grow two Wheat in this fashion,
(mouse equivalent) on a Cow and then repeat on another Cow. Make sure both Cows are near each other and they'll race with hearts of love. Achievement unlocks.
Hoe Recipe (Plank/Ore, Plank/Ore, Empty, Empty, Stick, Empty, Empty, Stick, Empty)