For the stock, when you roast something, chicken or whatever, if you have space in the oven add another pan and roast the bones or vegetables, careful not burn them, you keep for stock before boiling them, you get deeper flavour and a nice colour.

It’s strange because mold usually appears on top, where there’s air. But anyway I wouldn’t eat it.

This is the one I use, it’s simple: https://www.recipetineats.com/butter-chicken/