The impact of raindrops on the loose soil tends to transfer fine clay particles into the tiniest soil spaces, sealing them and producing a surface that allows very little water penetration.

Restaurant versions usually come in a clay or iron pot, with about 100 chilis floating on the surface of the bright red broth, and a few pieces of beef poking through.

They then pour on the liquid glaze and let it run over the clay surface, making any kind of decorative pattern that they want.