Start by dicing the yellow onion and mincing the garlic cloves. In a mixing bowl, combine the ground beef, egg, salt, black pepper, dried onion, breadcrumbs, and Dijon mustard. Use your hands or a spatula to mix gently until everything is just combined.

Once your mixture is ready, divide it into four equal portions for shaping. Roll each portion into a ball and then flatten it to about ¾ inch thickness.

In a large skillet, heat 1 tablespoon of olive oil and 1 tablespoon of unsalted butter over medium-high heat until shimmering. Carefully place the patties in the skillet, ensuring they are spaced apart. Sear the patties for about 5 minutes on each side.

Using the same skillet, reduce the heat to medium. Add the diced onion, minced garlic, salt, pepper, and dried thyme. Cook for about 3 minutes until the onions are soft.

Deglaze the skillet by pouring in ½ cup of dry white wine, scraping up any flavorful bits. Allow to simmer for about 2 minutes. Stir in ½ cup of heavy cream and bring to a gentle boil.

Return the cooked Salisbury steaks to the skillet, making sure they are well-coated in the sauce. Simmer for 5 minutes to allow the flavors to meld.