Make the chicken: adjust the oven racks so one is in the middle position and preheat the oven to 350°F.
Combine the stock and mole in a bowl. Smash and stir the mole with a whisk or fork to break it up and dissolve it. Season the chicken with the salt.
Coat a Dutch oven or ovenproof skillet with oil and heat the oil over medium-high heat until it slides like water in the pan and is sizzling hot but not smoking, 2 to 3 minutes. Add the chicken thighs, skin-side down, and cook until they are deep brown, about 5 minutes. Turn the chicken and cook for 2 minutes on the second side. Pour the mole-stock mixture around the chicken, adding enough so it comes halfway up the chicken; you may not use all the stock mixture. (Throw it out or use it in place of some of the water to make the teff.) Cover the pot and put the chicken in the oven to cook for about 1½ hours, until it is fork tender.
Remove the pot from the oven, uncover, and let the chicken rest in the liquid until it’s cool enough to handle. Shred the chicken into a small saucepan; throw out the skin and bones. Skim the fat off the braising liquid with a spoon or ladle, discard the fat, and pour the remaining liquid into the saucepan with the chicken. Bring the liquid to a simmer over high heat. Reduce the heat to maintain a simmer and cook the chicken and sauce together until the sauce has reduced and the chicken and sauce are one, about 10 minutes.
Make the the teff: combine the mole, salt, and 2½ cups water in a small saucepan. Smash and stir the mole with a whisk to break it up and dissolve it. Bring the liquid to a boil over high heat. Rain in the teff, stirring with the whisk as you add it. Reduce the heat to low, cover the pan, and simmer until the grains are tender and thick, like loose polenta or porridge, about 30 minutes.
Assemble the bowls: season the avocado with the juice of the lime and salt. Spoon the teff into four serving bowls and pile the shredded chicken on top. Put the avocados on top of the chicken. Garnish with the crema, sesame seeds, and onion slices.