Why Do Cats "Make Biscuits" With Their Paws?
When a cat "makes biscuits", she stretches out the digits on her front paws and pushes them downward as if she were kneading dough.
When kittens are nursing, they knead their paws against Mom, either as a sign of contentment, or to encourage milk flow. When they mature, they may knead against humans, toys, beds, blankets - anything is fair game.
This behavior shows contentment and pleasure, and is often accompanied by purring.