Grate the cucumbers on the big holes of a box grater. Squeeze the grated cucumbers with your hands and reserve the liquid (you should have about 1/2 cup of the brine, add another 1/2 cup of the brine from the jar with cucumbers, you should have 1 cup of liquid/brine in total). After you have squeezed out the water you should have about 1 2/3 cups of grated cucumbers.
Grate the carrot on the small holes of a box grater, cut the potatoes into small cubes (about 1/2-inch / 1.5 cm), finely chop the onion.
Heat the butter in a medium pan and add the cucumbers, cook over medium heat for about 5 minutes, stirring from time to time. Add them to the pot with broth.
Add another tablespoon of butter to the pan, add the onion and carrot. Cook over medium-low heat for about 5 minutes or until the onion is soft. Add the content of the pan to the pot with broth and cucumbers.
Add potatoes to the pot, bring to a boil, and cook for about 10-15 minutes or until the potatoes are soft.
Add the cucumber's brine (juice), add it gradually, and taste the soup making sure it's not too sour or not sour enough for you.
Take the soup off the heat.
Temper the cream: pour the cream into a cup, add a couple tablespoons of soup, stirring after every added tablespoon, then add the tempered cream into the pot.
Season the soup with salt and pepper to taste.
Stir in chopped dill.
Enjoy!