In the morning: put beans in a large bowl and cover beans with abundant water. It's better to soak them in too much than too little water. The beans will absorb a lot and you want to make sure they are submerged in water the entire time they are soaking.
In the evening: Peel and finely chop the onion and peel and crush the garlic.
Drain and rinse beans very well and then put in a large pot. Fill up with fresh water until about 2 inches above the beans. Add chopped onion and crushed garlic and about a teaspoon of salt. Bring to the boil and once boiling reduce to simmer and cook beans for about 4 hours. Add salt if necessary. Store in fridge.
The next day:
For the salsa:
Peel and wash tomatillos, leave as whole but cut out the hard top middle white section like you would with a strawberry. Be careful because the white part is very hard but the tomatillo's flesh is soft and the knife slips easily.
Peel garlic and wash and deseed jalapeño chiles.
Place tomatillos, garlic and chiles in a pan with lid and add about an inch of water.
Bring water to the boil and once boiling reduce heat to simmer and cover the pan.
Cook until tomatillos are very soft (about 30 minutes).
Wash cilantro and cut off bottom part of stalks.
Add cooked tomatillos, garlic, chiles and about half a teaspoon of salt to a blender and blend for about 30 seconds, then and add washed cilantro and blend until no big bits are left and the salsa is pourable.
For the tacos:
Reheat beans and season with salt again if necessary.
Heat a non-stick pan over medium heat, once hot warm up tortillas (about 1 minute per side). Add beans to taco and serve with queso fresco on top (omit for vegan version) and freshly squeezed lime juice and salsa verde.