In a large bowl, mix together ground beef, breadcrumbs, grated onion, heavy cream, egg, salt, and pepper until just combined.

Divide mixture into 4 equal portions and form into patties about 1/2 inch thick. Set aside.

Heat a nonstick skillet over medium-high heat. Cook patties for 4–5 minutes on each side until browned and cooked through. Remove and set aside.

In the same skillet, melt butter over medium heat. Add diced onion and cook until softened and golden, about 5–7 minutes.

Add garlic and cook for 20 seconds until fragrant. Season with salt and pepper.

Add flour and stir well, cooking for 1 minute to eliminate the raw flour taste.

Lower heat to medium-low and gradually whisk in chicken stock, then heavy cream. Continue to whisk until sauce thickens.

Stir in 1 tablespoon chopped dill and return patties to the sauce. Let simmer for 4–5 minutes.

Taste and adjust seasoning. Garnish with remaining dill and serve warm.