Must be Clan of the Squirrel. You need 1,000 of each Ingredient, 850ish Food, and at least 8 cooks (7+Warchief). Each Stove built will increase the amount of ingredients you can hold by 200.
Warchief can count as 1 cook and does not occupy a Cook slot.
Each Stove built can house 1 Cook, upgraded can house 2 cooks.
Ingredients are gathered passively from zones, different zones provide different resources.
Once you have 1000 of each Ingredient, 8 cooks, and 850 food click on one of your Stoves and choose the Banquet of Valholl. The cooks and Warchief will begin cooking the Banquet which will take several in game months. Once the feast is complete, victory is achieved.