Heat a soup pot over medium high heat, and melt the margarine. Add the onions and a tiny pinch of salt, and saute until they’re softened and translucent, about five minutes.
Add the garlic and thyme, and saute for about a minute, or until fragrant.
Add the celery and give it a good stir. Saute it for about 8 minutes or so, until the celery starts to soften a bit. Sprinkle the flour in and give another good stir. You want to cook it a bit until it’s not super white. If it starts to get hard to stir, pour in a little broth. Once you have the flour incorporated, pour in the veggie stock.
Bring the mixture to a boil and then partially cover the pot and reduce the heat. Simmer for about 20 minutes, stirring occasionally, until the celery is tender.
Transfer the soup to a high-speed blender and puree. Depending on the size of your blender you made need to do this in batches. You can also use a stick blender.
Taste for seasoning and serve. You can garnish with some fresh thyme or celery leaves. This also keeps well in the fridge.
