Nothing to learn and nothing extra to farm. The birthday hat has no blueprint of its own: it is a skin of the candle hat, which every player can craft from the start, and the bill on the calculator is that hat's, down to the cloth and the animal fat inside the low grade fuel. Own the skin and the birthday candle shows up when you craft a candle hat, with no bench needed.
The row changes nothing: the same light, the same fuel, the same return from the recycler. So the choice is looks, and a night farmer gets nothing from it that the plain hat lacks.
The fuel leftovers work the same way too, so queue it with the plain hats for the group.
Questions
Birthday Candle Hat ×10: how many resources?
Cloth ×163, Animal Fat ×39.
Which workbench does Birthday Candle Hat need?
None: it is crafted by hand.
How long does Birthday Candle Hat take to craft?
25 s for one, every step included.
How much scrap does researching Birthday Candle Hat take?