Melt butter in 1 tablespoon oil in a Dutch oven or a soup pot on low medium heat.
Add diced onion and cook, stirring often, until softened, about 3-5 minutes.
Add diced carrot and cook 3 more minutes, stiring.
Finally, add minced garlic and cook until fragrant, about 1 minute.
Add diced potatoes and broth, and bring to boil.
Partially cover the pot and cook for 10 minutes.
Now add diced or grated pickles and pickle brine (if using) and cook 10 more minutes.
Check potatoes for doneness. If soft, stir in cream and chopped dill.
Taste and season with salt and pepper, if needed. You can also add a little more pickle brine, if you prefer brinier soup.