They cry and hang on your legs.
As every woman has observed, cooking is a two handed operation. No matter how tenderhearted you are about letting your baby or toddler koala bear onto you all day long like a suction cup or a piece of velcro, you cannot hold them while you cook. You really cannot have them stuck to you in a baby sling or carrier either, because you can't see over them to see whether you are about to chop a carrot or a finger.
I shove my high chair up to the counter and let them stand in it facing the counter. It's like a tall stool that almost has sides.
Once the child is old enough to stand without crashing most of the time, they can stand in the high chair and help. This is probably violating 16 safety codes recommended by the pediatric association. But the pediatric association people are in climate controlled offices with no tiny people hanging on their legs crying while they try to give their power point presentations. This is real life. I haven't had anyone fall or paralyze themselves yet and it keeps the toddler occupied while you cook. I give them a tiny portion of whatever I'm working on to make them feel big. When they get old enough, I have an un-sharp knife that they can pretend to use to chop stuff up.
You're their whole world. They're not trying to ruin your day or sabotage your cooking. They just want to be right there with you because you're where the fun is, you're where the action is, and you're where the love is.