Avocados mashed into guacamole
To make guacamole the way the Aztecs did, take one ripe avocado and cut it in half, and use a knife or a fork to pry out the seed. Scoop out the yellow fruit into a bowl (or a stone mortar like the one in the picture) and mash it with a fork (or a stone pestle). Add half a chopped onion, a little chopped chili pepper (depends how spicy you like it!), half a chopped tomato, a pinch of salt and a spoonful of chopped fresh cilantro. Mix it up and eat it on tortilla chips!
Modern guacamole recipes often have you add a couple of spoonfuls of lime juice or lemon juice. That helps keep the guacamole from turning brown from oxidization so quickly. But limes and lemons come from India originally. The Aztecs didn't have them, so if you want to make Aztec guacamole leave out the lemon juice!
(more about how to grow one)
For another avocado project, plant the seed in a flower pot and watch it grow into an avocado plant. Unless you live in a very sunny, warm place like Central America, though, your avocado plant won't ever get any avocados on it - sadly.
For more information about avocados and guacamole, check out these books from Amazon or from your library:
South American food
Kidipede - History for Kids