Heat the oil in the Instant Pot on Sauté. With a stovetop pressure cooker or soup pot, heat the oil over medium flame. Stir in the onion, sauté for 5 minutes, until the onion is translucent. Add the vegetable broth, lentils, carrots, beets, bay leaves and thyme.
In the Instant Pot, manually set the time to 6 minutes. Quick release the pressure using the top vent.
For conventional pressure cooker—bring to pressure and cook for 6 minutes. Quick-release the pressure under cold running water.
For stove-top cooking, simmer on low heat for about ½ hour, or until the beets are very soft.
Remove the bay leaves and thyme sprig. (see note!) Puree the soup until smooth and velvety. Puree right in the cookpot, or of you don’t have an immersion blender, puree the soup in a blender. (Do this in 3 batches, as the steam from hot soup in a full blender forces the lid off, making a huge mess. Been there, done that.)
Put the miso in a small bowl. Add ½ cup of the pureed soup and stir to dissolve the miso well. Stir the miso mix back into the pot. Heat gently but do not boil. (see note)
Serve simply, garnished with chopped parsley.