Save your large egg shells next time and plant with seeds. Once plants are large enough, just transfer the whole egg into the ground. The shell is actually a great fertilizer and the roots will be able to break right through.
How to Grow an Avocado Tree : Eat an avocado (fun part) - Clean-off the pit - Suspend it over a dish of water with toothpicks (half-submerged) - Wait 3 to 6 weeks for it to sprout. Seriously going to try this