Sometimes it can try your patience, but the results are worth it as they become engaged and love food.
Start off by getting them up on the bench with you and cracking eggs, mixing flour, topping beans, shelling peas, simply putting salt in is a really good one, they love putting a putting a pinch of salt into things.
Putting things into a bowl from a board like potatoes, really basic stuff is a great start.
Boys and girls love that it's a really tactile experience, it's like playing in a sandpit and it's something they naturally enjoy. We're often told we shouldn't play with our food when actually you should play with it, it's fun.