Depending on what type of citrus being used to make yuzu kosho, the number of citrus will change since sizes really vary. Yuzu is hard to come by outside of Japan and I normally use limes or Meyer lemons. You can use microplane or skin the citrus and mince. The fruit itself is not normally used but I like to add some to loosen the mixture a bit.
Hot green chile pepper (preferably Japanese, Thai, etc) but I've used serrano and New Mexico. New Mexico/anaheim makes milder version. Stem, remove the membrane and mince peppers using gloves to protect your hand.-
Salt - 12% of weight of combined citrus skin and pepper.
There are all variations. Some are ultra smooth and made by blender method. Add skin, pepper and salt. I like mine with more texture so I use motar and pestle method.
For red variety, add some Korean style red pepper flakes called kochugaru to your taste to the mixture.
3-4 yuzu or 2 limes/meyer lemons
5 hot green chile pepper of your choice. You can adjust the quantity to your taste
salt (12% of weight of mixture)
Put into a glass jar and refrigerate. Keeps forever.