In a large mixing bowl, gently combine the grated onion, ground beef, breadcrumbs, salt, pepper, heavy cream, and egg. Mix until just combined.

Divide the mixture into four equal portions and shape each into a patty about ¾ inch thick. Make a slight indentation in the center of each patty.

Heat a skillet over medium heat and add olive oil and unsalted butter. Once melted, add patties and sear for 4-5 minutes on each side until golden brown.

Remove the patties and add diced onion and minced garlic to the skillet. Sauté for about 2 minutes until the onion is translucent.

Sprinkle salt, pepper, and all-purpose flour over the sautéed onions and garlic. Stir for about 1 minute to cook the flour slightly.

Slowly pour in the low sodium chicken broth, stirring to combine with the roux. Scrape the skillet to incorporate any stuck bits and let it simmer for about 2 minutes.

Stir in the heavy cream and fresh dill, bringing the sauce to a gentle boil. Reduce heat and let simmer for 1-2 minutes until thickened.

Return the seared patties to the skillet, nestling them into the sauce. Simmer for an additional 5-6 minutes until heated through.