Melt the margarine in a heavy-bottomed saucepan and sauté the chopped onions for 2 minutes over medium to high heat. Then reduce the heat and fry for another 5 minutes with the pot closed.
Stir in the flour and wait, stirring constantly, until the roux is lightly browned, then add the vegetable stock and chopped herbs and bring to the boil briefly. Simmer over low heat for 20 minutes. Take the soup off the stove and puree briefly.
Then put it back on the stove and add the cheese. Stir until the cheese has melted.
Garnish the soup with the chives rolls before serving.