Instructions:
Rinse your beans well and remove any broken pieces. Add the beans, salt, and onion to the pressure cooker and cover with the water. Close the lid and heat on high until the safety valve closes on the pot and the pressure gauge begins to rock gently and consistently (or if your pressure cooker doesn’t have a rocking gauge, follow the directions that came with the pot). Allow the beans to cook for 20-25 minutes.
While the beans are cooking, remove the stems of the tomatoes and roast them under the broiler in the oven with the onion, chiles and optional garlic. Turn them to the other side when you notice them getting darkened. Remove from the broiler and set aside.
On the stovetop, cook the bacon in a frying pan until it is moderately crispy. Remove from the pan and drain on paper towels. Tear the bacon into bite-sized pieces and set aside.
Next, cook the chorizo over medium heat in a frying pan, making sure to break up the meat into small pieces. Be sure not to overcook the chorizo. Drain on paper towels if necessary.
By this time, the beans should be halfway done. Remove the pot from the heat. If desired, you can gently alleviate the pressure by using an oven mitt to set the pressure gauge slightly off-kilter to allow steam to escape until the safety valve unlocks. Caution: it will be very hot and will burn you if you don’t protect yourself with an oven mitt. I like to also use a kitchen towel to catch the steam carefully in addition to wearing the mitt. If you’re not confident about trying this method, don’t worry – just let the pot sit after you’ve removed it from the heat until you hear the safety valve unlock. It will take a little longer that way, but if you’re at all nervous about safety because you’re a first-time pressure cooker user, just let it rest and cool on its own.
Add the roasted tomatoes, chiles, onion and optional garlic into the blender and puree until completely smooth. 
Open the pressure cooker once the safety valve has unlocked. There should still be a decent amount of liquid in the pot covering the beans. If not, add a little water until the beans are completely covered.
Add the mixture from the blender to the pot and then the beer; stir once, throw the small sprig of cilantro on top and close the pot back up securely. Put it back on medium-high heat until the pressure gauge rocks gently and consistently again (it should not spin or spit liquid; if it does, the heat is too high). Reduce the heat just slightly and cook for another 25-30 minutes.
Remove from heat and allow to cool using the same method as before. Once you open the pot, the beans are ready to be served; just add salt to taste.
Garnish with finely diced white onion, serrano chile, crushed chicharrón and if desired, a few fresh cilantro leaves.
