In a heavy-bottomed soup pot or Dutch oven, melt the butter over medium heat.
Add the chopped onion, carrot, cubed pumpkin, and caraway seeds.
Sauté for 8–10 minutes, stirring occasionally, until the pumpkin is tender and starts to caramelize.
Pour in the vegetable stock, bring to a simmer, and cook for 20 minutes, allowing the flavors to meld and the vegetables to become completely soft.
Remove the pot from the heat and stir in 2 cups (480 ml) of the cold milk. This helps cool the mixture slightly before blending.
Carefully transfer the soup to a blender in batches and purée until completely smooth. Return the smooth soup to the pot.
Stir in the remaining milk until you reach your desired consistency.
Gently reheat the soup over low heat, but do not let it boil.
Season generously with salt and pepper to taste.
Serve hot, garnished with a sprinkle of smoked paprika or crumbled chipotle chili.