In a large, heavy bottomed pot, melt the butter over medium heat. Add the carrot and onion and sweat until the onion is translucent and the carrots are softened, about 10 minutes.

Add the rice and tomato paste and cook, stirring, about 1 minute. Add the stock and salt and bring to a boil. Reduce heat to a simmer and simmer until the rice is tender, about 12 minutes.

Use an immersion blender to puree the soup until smooth. (Alternatively, the soup can be pureed in batches in a blender-- if you use this approach, allow the soup to cool a bit first, and vent the blender lid to avoid explosions.)

Stir in the milk to the pureed soup, and add more stock if the soup is too thick. Heat until warmed through.

Serve the soup hot topped with freshly cracked black pepper and fresh herbs. Drizzle with a bit of heavy cream for a fancy look!