Celery and Potato Soup for 4

Scaled to serve 7

87.5 g of margarineheattosssimmer 30minblend
787.5 g of celerycut into 1.5cm pieces
481.2 g of potatoespeeled, cut into 2.5cm cubes
1575.0 ml of chicken stock
1.8 bouquet garni
1.8 salt and pepper