Warm the olive oil in a large Dutch oven over medium heat. Add in the chopped onion and jalepeno and soften for about 8 minutes, stirring occasionally. Take care to make sure it does not brown.
Add in the poblano, tomatillos, garlic and water, stir, then cover and allow to soften for 12-15 minutes. Take the lid off and continue cooking, until most of the water has been absorbed, but taking care not to let anything in the pot brown.
Remove from the heat and allow to slightly cool. Transfer to a blender and puree until very smooth. Add in the salt, vegan mayo and cilantro and puree again until very smooth. You’ll want the sauce to be smooth and a little thin.
Transfer to a container and chill before serving.
Recipe by Olives for Dinner at https://olivesfordinner.com/2016/06/creamy-poblano-cilantro-sauce.html