In a large pot pour the water or chicken stock, add frozen green peas and celery stick. Cook for 20 minutes on medium heat until peas will be soft.
Cool off a little before blending.
Add peas with some water to the blender and blend until smooth.
Add everything back to the large pot.
Melt butter on the pan, add flour and cook for few minutes mixing often. Add it to the soup and mix everything nicely. Cook on low-medium heat for 10 minutes. Add chopped dill, salt and pepper. You can add cooked chopped celery stick.
Serve with potatoes, rice, pasta or without anything.