Heat a medium or large pot over medium-high heat with the ¼ cup of olive oil.
Once the oil is hot, add the onion and garlic.
Cook until the onion and garlic have browned, flipping as needed to get all sides.
Drain, but do not rinse your beans, then add them to the pot.
Cover with 1” of water.
Bring to a boil, reduce to a low simmer, and cook until the beans are tender but not falling apart, 20-25 minutes.
If you have a lot of liquid left, use a slotted spoon to remove the beans, bring the broth to a boil, and cook until there is enough liquid just to cover the beans. Add the beans back in and continue as usual. You can leave the added broth and have a bowl of extra brothy beans- it’s up to you!
Turn off the heat once you have tender beans and flavorful broth.
Place 1 tablespoon of miso in a ladle and skim a bit of broth into the ladle. Using a spoon, stir the miso and broth together to loosen the miso–this technique helps the miso incorporate a bit easier.
Dip the ladle into the pot of beans, add 1 tablespoon of vinegar, and stir to distribute evenly.
Taste and add more miso, vinegar, or a pinch of kosher salt to find a balance you enjoy.