Peel and chop the onions, celery and carrot finely.
Peel and cut the potatoes into 2-3 cm cubes (1 inch)
Heat a large pot on medium-high.
Toss the butter into the pot.
Once the butter is melted and bubbly, top with the onion.
Stir the onion till translucent, then add the carrot and celery.
Allow to soften, then add the potatoes.
Immediately, top the pot halfway up with water and stock. Bring to a boil, then reduce to a simmer until the potatoes are cooked (about 10-12 minutes, depending on the size of the chunks).
Pour in the cream. Turn up to medium-high heat.
Add the cooked chicken.
Sprinkle with sea salt and pepper (to taste).
Once the chicken is piping hot, the soup is ready to serve.
Spoon into bowls and serve.