The Witches' Coven is both a building and recipe.
The Witches' Coven takes up a 2x2 space making the happiness and culture worth 1762h / 176c per square. It can be sold for 6000 silver. It is acquired through the Workshop. This is the fourth set of recipes you learn.
Below are the rewards and price in gold to be completed instantly for each sub-recipe.
2x Gravel - Quarry (30 minutes to produce)
1x Stack of Logs - Lumber Mill (30 minutes to produce)
1x Wooden Barrel - Lumber Mill (2 hours to produce)
3x Onions - Garden (2 hours to produce)
2x Garlic - Garden (4 hours to produce), Vegetable Farm (2 hours to produce)
1x Carrot - Garden (15 minutes to produce)
1x Oil - Mine (8 hours to produce)
5x Minerals - Mine (30 minutes to produce)
2x Stack of Logs - Lumber Mill (30 minutes to produce)