Creamy Chicken and Tortellini Soup

carrots (peeled and chopped into chunks)

medium sized potatoes (peeled and chopped into small chunks)

celery (sliced)

good pinch of salt and pepper

sprigs of thyme or 1 tsp dried thyme

chicken stock (water plus 3 stock cubes is fine)

butter

large onion (peeled and finely chopped)

plain/all purpose flour

milk (half or full fat)

cooked chicken breasts (shredded (or use the meat from a shop-bought rotisserie chicken))

lemon juice

pack of fresh tortellini ( I used Giovanni Rana Ham and Cheese tortellini)

few sprigs of fresh thyme