Let the chicken thighs come to room temperature. Use a paper towel to pat dry. Place to the side.
Preheat the oven to 400°. To clean the leeks, slice, and let them soak in a bowl of water to remove dirt from its crevasse. Using your hands, swirl the leeks, and pull the slices from the water. Do not strain the water with the leeks- that would defeat the process of cleaning them. Let the cleaned leek slices rest on a dishtowel.
Peel the carrots and potatoes, and cut them along with the onion and one garlic clove. Over medium-high heat, add 2 tablespoons of olive oil into a dutch oven, and sear the leeks, onions, carrots, potatoes, and garlic clove. Add a generous pinch of salt. Cook for about 8 minutes.
To make the broth, collect all of the scraps from the vegetables, and cook with 8 cups of water over medium-high heat. Add a generous pinch of salt and fresh cracked pepper. Let it come to a boil, reduce the heat to medium, and cover with a lid. Let it cook for 20 minutes. Strain the broth into a bowl, and discard the cooked scraps.
On a cooking sheet, add the tomatillo and the remaining 2 garlic cloves, with a drizzle of olive oil, around 2 tablespoons. Cook until the tomatillos plumpness deflates and chards a bit, about 8 minutes.
Pour the stock into the cooked vegetables. Add the chicken pieces and bay leaves. Give it a good turn. Let it come to a boil, then lower the heat, and cook covered for 35 to 45 minutes.
Directly add the tomatillos-garlic, along with its juices and oil to a blender. Blend until smooth.
Add the tomatillo to the soup, give it a good turn, and put the lid back on. This may be added at any time while cooking. After 45 minutes, the chicken will easily fall apart with a ladle. Check for seasoning by adding more salt and pepper. Can easily be stored in airtight containers for meal preps and/or freeze for up to a month. Enjoy!
Notes
Crockpot or Instant PotSimply follow the above instruction, but cook the stock in a separate pot or use store-bought vegetable or chicken stock.