Instructions

1. Bring 6 cups water to a boil in a large saucepan over high heat. Meanwhile, while rinsing them under cool running water, remove the husks from 1 pound tomatillos. Trim off any attached stems with kitchen shears if needed. Trim the stems from 2 medium serrano peppers. For a spicy sauce, leave whole. For a milder sauce, halve lengthwise, then scrape out the seeds and membranes with a small spoon.
2. Add the tomatillos, serrano peppers, and 1 teaspoon of the kosher salt to the boiling water. Cover, reduce the heat to low, and simmer until the tomatillos and serranos darken in color and the serranos are knife-tender, 6 to 7 minutes.
3. Meanwhile, peel and coarsely chop 1/2 large white onion. Smash and peel 3 garlic cloves. Place the onion and garlic in a blender or food processor fitted with the blade attachment. Add 1/2 medium bunch fresh cilantro, the remaining 1 teaspoon kosher salt, and 1 teaspoon bouillon paste.
4. When the tomatillos are ready, turn off the heat. Scoop out 1/2 cup of the cooking liquid and add to the blender. Blend until as smooth as possible. Using a slotted spoon, transfer the tomatillos and serranos to the blender, and blend again until desired consistency.
5. Heat 2 tablespoons vegetable oil in a large frying pan over medium heat until shimmering. Remove the pan from the heat. Using a lid to shield yourself from oil splatter, carefully pour in the tomatillo mixture. Return to medium heat and bring to a low simmer. Simmer, stirring occasionally, until it reduces slightly and darkens in color, 5 to 7 minutes.