In a large bowl, combine the ground beef, breadcrumbs, grated onion, salt, black pepper, heavy cream, and egg. Gently mix until just combined, then shape into four patties, about ¾ inch thick.

Heat a large skillet over medium heat, add olive oil and unsalted butter. Once melted, add the patties and cook for 4-5 minutes on each side until browned and cooked through.

In the same skillet, add minced garlic and sauté for 2 minutes. Add salt, black pepper, and flour, stirring for 1 minute.

Pour in chicken broth and scrape the skillet to release browned bits. Simmer for about 2 minutes.

Reduce heat to low and stir in heavy cream and chopped dill, simmer for 1-2 minutes to thicken.

Return the patties to the skillet, cover, and simmer for 5-6 minutes, garnish with additional dill and black pepper before serving.