Egg Versus Wank

Listen up, buttercup! This joke is all about wordplay. "Beating an egg" is what you do when you're cooking, you uncultured swine. But "beating your meat" is a slang term for jerking off. So, the joke is that the difference between an egg and a wank is that you can "beat" an egg in cooking, hinting at the double meaning related to masturbation.