Prepare the Ingredients:
Dice 3/4 of the onion and set aside 1/4 for salsa
Mince 5 garlic cloves and set aside 5 whole cloves for salsa
Remove and discard papery husks from tomatillos
Rinse tomatillos and cut into wedges
Dice green bell pepper, removing seeds and membrane
Remove stems from jalapeños and serrano pepper
Build the Soup Base:
Heat 1-2 tablespoons avocado oil in large Dutch oven over medium-low heat
Add diced onion (3/4), bay leaf, and pinch of kosher salt
Sauté until softened and lightly golden, about 5 minutes
Add diced bell pepper and continue cooking for 2 minutes
Stir in minced garlic (5 cloves) and cook until fragrant, about 2 minutes
Add oregano and ground coriander
Continue sautéing for 2 minutes, stirring constantly to toast spices
Add Tomatillos and Beans:
Add tomatillo wedges to pot
Sauté until they turn brighter green and begin to soften, about 4 minutes
Add drained and rinsed cannellini beans
Add 3 cups vegetable broth
Add fresh thyme sprigs
Bring to gentle simmer
Cover with lid and cook for 20 minutes
Make the Salsa Verde (while soup simmers):
Roughly chop reserved 1/4 onion
Lightly crush 5 remaining garlic cloves with flat of knife
Roughly chop jalapeños and serrano pepper
Heat 3 tablespoons avocado oil in small saucepan over medium-low heat
Add chopped onion, crushed garlic, and chopped peppers
Cook for about 4 minutes until garlic and onion are tender and golden
Remove from heat and allow to cool slightly
Transfer cooked vegetables and oil to blender
Add cilantro, generous pinch of salt, 3 ice cubes, and 3 tablespoons water
Blend on high until thick and smooth
Finish and Serve:
After soup has simmered 20 minutes, remove thyme sprigs and bay leaf
Taste soup and adjust salt as needed
Ladle hot soup into serving bowls
Top each bowl with generous spoonful of fresh salsa verde
Add sliced avocado and other desired toppings
Serve immediately with baked tostones or crusty bread
Storage: Soup keeps refrigerated for up to 5 days or frozen for 3 months. Make salsa fresh when serving for best color and flavor, or store separately in airtight container for up to 3 days.
Heat Adjustment: Remove pepper seeds for milder soup. Leave seeds in for medium heat. Add extra peppers for spicier version.