In a medium saucepan combine the peeled red potatoes, stock, onion, and white pepper. Bring water to boil then reduce heat. Simmer uncovered about 20 minutes or until the potatoes are fork tender. Mash the potatoes slightly; DO NOT drain.
In a screw-top jar combine 1/2 cup milk and the flour; cover and shake vigorously. Add the mixture to the saucepan then add the remaining milk. Cook and stir until bubbly for approximately 1 minute but be careful not to burn.
Finally, stir in the bleu cheese (reserve 2 tablespoons for garnish), butter and fresh parsley. Keeping stirring the soup until the cheese and butter melt. At this point you can choice to puree the soup or not. Top each serving of soup with diced tomatoes, green onion slices, sprinkle of bleu cheese and garnish of fresh parsley.