Heat your oven to 135°C.
Heat a small pan over medium heat and toast the whole spices for 1 minute, until fragrant. Remove and blend in a spice blender of pestle with the remaining spices.
Heat a large, heavy bottomed pot over medium high heat and add some oil. Sear the shortribs off on all sides until nicely browned and set aside.
Roughly chop the one and a half of the white onions and add to the pot (the remaining half onion will be used later to garnish). Fry of for 3-5 minutes, until nicely browned.
Chop the coriander stems and peel the garlic cloves and add them. Fry off for 2 minutes or so.
Quarter the tomatoes and add to the pot. Cook off for around 5 minutes, until softened and breaking down.
Add the tomato puree and fry it off for 2 minutes, mixing well to combine.
Add the dried chillis and chipotle chillis along with the spices. Cook off for 2-3 minutes, untl the dried chillis and softening and toasting.
Add the stock and the juice of one of the limes and blend until smooth.
Add the ribs back in and cover in the sauce. Put the lid on the pot and put it in the oven for 4.5 hours.
Remove the ribs from the sauce once cooked. Remove the bone (they should slide out cleanly) and shred with 2 forks. Add in a few ladles of the sauce and mix.
Grate your cheese, dice the remaining half a white onion and chop the coriander leaves.
Heat up a non stick frying pan on medium heat.
Take a tortilla and dip it into the birria sauce. Place it straight onto the pan.
Add some shredded beef, cheese, white onion and coriander on one half and flip the other half over.
Fry it off for a minute or so then flip it. Fry on the other side for a minute and remove and put on a plate. Repeat for all the tortillas.
Pour the remaining sauce into 2 bowls and serve with the tacos. Quarter the remaining lime and serve 2 slices with each portion. Garnish the tacos and sauce with the remaining white onion and coriander leaves and serve!