Recipe: Just use white portland cement and sand...1 part cement to 3 parts sand...and add a couple of cap fulls of concrete acrylic fortifier (Quikrete makes one). Add enough water to make the mixture thick enough so it doesn't run off the leaf. I made the mistake once of adding more sand when the mixture was too thin. It made the concrete weak and the leaf crumbled when it dried.
There are many different ways and recipes for making concrete leaves. Check the Internet!
A few notes: You don't have to paint the leaves. You can attach a hanger on the back of the leaf (while it's wet) in case you decide to hang it. The more sand you mound, the more "cupped" the leaf will be. Some people like them flat, but cupping them a bit makes them a little more realistic.
I'll gladly answer any questions you may have.
