Gather all your ingredients and chop the onion, carrots, and celery into small, even pieces to ensure they soften evenly.
In a large heavy-bottomed pot, melt the butter over medium heat until it’s frothy and begins to smell nutty, about 2-3 minutes.
Add the chopped onion, carrot, and celery to the pot. Cook, stirring often, until the vegetables soften and release a sweet aroma, about 8-10 minutes.
Stir in the chopped chicken thighs, season with salt, pepper, and thyme. Cook until the chicken is just cooked through and lightly browned, about 5-7 minutes.
Pour in the chicken stock, bringing the mixture to a gentle simmer. Let it bubble softly for 15 minutes, uncovered, allowing flavors to meld.
Stir in the heavy cream, then reduce the heat to low. Let the soup simmer gently for another 10 minutes, until it thickens slightly and develops a velvety consistency.
Taste the soup and adjust the salt and pepper as needed. Finish by stirring in a splash of lemon juice to brighten the flavors.
Ladle the hot, creamy soup into bowls, garnish with chopped parsley, and serve immediately for a cozy, comforting meal.