Consommé is supposed to be a super-clear, full-of-flavour liquid, therefore the stock or bouillon needs to be clarified. The first secret of making the clearest possible stock is the simmering and stirring, this will bring up the filth to the surface. Regarding to the internet, adding tomatoes will also help, thanks to the acid in it. The widely used method to remove all the solid bits from the liquid is using egg white: just simply stir it into the stock at the end of the cooking process and then filter it through a cheesecloth. The residue is the most disgusting yellowish, fluffy stuff (bin!) – and beneath you’ll have the clear liquid:
For a real, posh consommé you need to remove those lovely fat drops as well, which are floating on the surface. There are various methods for that, like simply refrigerating the liquid, so the solid fat could be removed easily from the top, or using parchment paper, which is another very DIY way, I like it much.
Kat said that some don’t like using egg white to clarify the stock, because it may absorb not only the solid bits but the flavour as well. Another way is gelatin filtration (this is a molecular gastronomy thing, the egg-method is way easier!). The idea behind is that the bulk water from a water based stock will turn into ice crystals below zero – right, very basic physic -, and the water associated with all the solutes, like gelatin, fat and other solid things will remain unfrozen on that temperature. BUT! this temperature is just cold enough to turn the gelatin into a stable network.
Now the magic is to freeze the whole thing as it is and then bring it back to just above zero (and to keep it there, which, let’s be honest, would be a real pain in The Average Household), so the bulk water can slowly thaw. On this temperature the gelatin network is still stable and will literally trap all the solutes (=undesirable stuff) but not the flavor molecules so if you for e.g. placed the frozen stock in a mesh strainer, the supermegaclear consommé will be dripping down.
Whoaaa, this was some serious shit, please forgive me. Hope you didn’t even get bothered with reading it. Even Kat uses the plain but perfectly working egg protein method at home, and we don’t care much about the golden fat droplets on the surface, because we simply love them. Those lovely little circles on the top make it all appetizing!