Begin by dicing one yellow onion and mincing two garlic cloves to release their aromatic essence. Set them aside for later use. In a large mixing bowl, combine ground beef, egg, breadcrumbs, dried onion, Dijon mustard, salt, and coarsely ground black pepper. Mix gently until everything is just combined.

Divide the mixture into four equal portions, shaping each into patties about ¾ inch thick. Make a slight indentation in the center of each one to help them cook through without puffing up.

In a large skillet, heat a tablespoon of olive oil and a tablespoon of unsalted butter over medium-high heat until shimmering. Carefully add the shaped patties, searing them for about 5 minutes on each side until they develop a beautiful golden-brown crust.

Once the patties are nicely browned, remove them from the skillet and set aside on a plate. Cover them loosely with foil to keep warm.

Lower the heat to medium and add the diced onion and minced garlic to the same skillet, scraping up any flavorful brown bits left behind. Season with salt, pepper, and dried thyme. Sauté for about 3 minutes until the onions are translucent and fragrant.

Pour in half a cup of dry white wine to deglaze the skillet, stirring to lift the brown bits. Allow the wine to simmer for about 2 minutes.

Reduce the heat to low and pour in one cup of heavy cream, stirring constantly. Bring the mixture to a gentle boil.

Stir in half a cup of grated Parmesan cheese and fresh horseradish, adjusting the horseradish quantity to fit your spice preference. Let simmer for another minute.

Carefully return the cooked Salisbury steaks into the skillet, spooning the creamy sauce over each one. Cover and let them simmer for an additional 5 minutes.

Garnish the Salisbury steaks with freshly chopped chives. Serve immediately, pairing them with creamy mashed potatoes or buttered noodles.