Preheat oven to 375°F.

In a food processor, pulse prunes and hot water until smooth. Pulse in oats and walnuts until a sticky dough forms.

Roll dough into 12 balls and place on baking sheet lined with parchment paper. Bake for 15 minutes.

Immediately after removing from the oven, tap each of them down with a glass to form a cookie shape and let cool.