The secret here is to use 1 cup less liquid than called for in the package soup instructions. This recipe assumes it wants 3 1/2 cups. Check your instructions and adjust accordingly. If you can't get white onion soup, leek and potato or any mild white soup will do.
Dilled Tuna Sauce
For two to three people, you will need:
1 package white onion soup
1 1/4 cups skim milk
1 1/4 cups water
1 (220 gram, or 7 oz) can tuna in water
1 teaspoon dried dill
Make up the onion soup with the skim milk and water. Cook for
the
amount of time specified on the package. The soup should be thick and
creamy.
While it cooks, open the tuna and drain off the liquid. When the soup
has cooked, stir in the tuna and the dill. Heat through.