Using a mandolin, thinly slice the zucchini in a large bowl. Sprinkle with salt and toss gently. Let stand for about 30-60 minutes.
Prepare the roux by melting the butter in a medium saucepot, over low-medium heat and add onion, sauté for 5 minutes until the onions are softened. Stir in the flour, combining with the butter and onions, and continue on low-medium heat, stir in vegetable stock or water and simmer for 4-5 minutes until it’s creamy and it starts to thicken.
Squeeze out the liquid from the zucchini, and add to the sauce. Then add and stir in sour cream, vinegar, dill, salt and pepper. Simmer for about 12-15 minutes until zucchini is tender. Taste and adjust seasoning if needed.
Transfer to a serving plate and garnish with paprika and dill. Serve with Hungarian patties or pork chops.
Note: Goes great with paprikash