Melt butter in a large pan over a low heat. Add onions and carrot and cook gently until soft. Add oats to pan and cook for about four minutes, stirring frequently. Add stock and bring to the boil. Simmer for 25 minutes. Add milk and heat through. Season to taste. Add chives or parsley, and a little cream if desired.
The above makes a thick broth – use less oats and more stock if you prefer a thinner soup. The addition of good undyed smoked haddock or smoked salmon makes a good alternative to Cullen Skink.