Prep the leeks. Cut off dark green tops and roots. Slice leeks in half lengthwise, then into half-moons. Rinse thoroughly in a bowl of water to remove any dirt trapped between layers. Drain well.
Sauté the base. In a large pot or Dutch oven over medium heat, add olive oil or butter. Once hot, add sliced leeks and sauté for 5-6 minutes until softened and fragrant. Stir in The Fit Cook Herb and Garlic Blend and cook for another minute to bloom the flavors.
Add potatoes, stock, and chicken. Add diced potatoes, chicken breasts, stock, and bay leaf to the pot. Bring to a boil, then reduce heat to medium-low and simmer for 18-20 minutes until potatoes are fork-tender and chicken is cooked through (165°F internal temperature).
Note: If you want to slow cook this recipe, I would add 7-8 cups of chicken stock and simmer for 1 hour or so until the liquid is reduced to 5-6 cups.
Remove chicken and blend. Reduce the heat slightly to stop the soup from simmering. Remove chicken breasts and bay leaf from the pot. Using an immersion blender, blend the soup until completely smooth and creamy. While the soup cools slightly, shred the chicken with two forks.
Pro-tip: for an even silkier result, add the soup to a high-powered blender. The result is phenomenal!
Stir in Greek yogurt and finish with chicken. Add about 1/2-1 cup of the soup broth to the Greek yogurt and mix well until it is pourable and fully incorporated. Then, with the immersion blender still processing the soup, slowly pour in the yogurt mix. This helps the yogurt remain silky and prevents curdling. The soup should be silky smooth with a beautiful pale, creamy off-white color.
Add the shredded chicken, then season with salt and pepper to taste.
Serve. Ladle into bowls and garnish with chopped fresh chives, fresh dill, and a light sprinkle of The Fit Cook Herb and Garlic Blend. Add an optional dollop of Greek yogurt on top for extra presentation.