TL: Only high-grade yukkuris are chosen by the buffet restaurant. All the seasoning paste comes from fresh yukkuris' paste filling. These yukkuris are tightly fixed on tables, with their head neatly cut open. Customers can dig out the paste as they want.
There's non-stop supply of paste, as the yukkuris are connected to pipes providing food to them. The remaining of other yukkuris made into cuisines are converted into their feed. This ensures that every of these seasoning-yukkuris contain sufficient paste.