Start by peeling the carrots and slicing them into thin rounds. Finely chop the onion and garlic. Grate the orange zest and freshly squeeze the orange juice. Heat the butter or olive oil in a large pot, then sauté the onion and garlic until translucent. Add the sliced carrots and cook for about five minutes, stirring occasionally. Pour in the vegetable broth and bring it to a boil. Reduce the heat and let the soup simmer for about 20 minutes, or until the carrots are soft. Blend the soup until smooth, using an immersion blender or a regular blender. Stir in the orange juice and zest, and season with salt, pepper, and a pinch of sugar. If desired, add heavy cream or crème fraîche for a creamier texture.

Serve the soup hot, garnished with fresh thyme or parsley. Enjoy with a slice of crispy baguette or some homemade croutons.