Step 1

Step 1 Heat oven to 350. Melt the butter in a large skillet or Dutch oven set over medium-high heat, and when it foams, add the onion and mushrooms. Stir to coat the vegetables with fat, season with salt and pepper and cook, stirring occasionally, until the onions are translucent and the mushrooms have started to brown, about 15 minutes. Transfer half the mushroom mixture to a large bowl, and set the skillet aside.

Step 2

Step 2 Make the meatloaf: Mix the panko into the mushroom mixture in the bowl, then add the meat, and mix again, making sure not to overhandle the meat. Add the egg and mix again.

Step 3

Step 3 Transfer to a sheet pan and shape the mixture into a rectangle. Bake until firm and nicely browned, approximately 40 to 45 minutes

Step 4

Step 4 Meanwhile, make the gravy: Return the skillet with the remaining mushroom mixture to the stove, and heat over a medium flame. When the mixture is hot and glistening, stir in the tomato paste and paprika. Cook, stirring occasionally, until the tomato paste just begins to caramelize, about 2 minutes. Stir in the stock and Worcestershire and cook until it begins to simmer.

Step 5

Step 5 Put the sour cream into a medium bowl and add to it 1/4 cup of the hot liquid from the mushroom mixture in the skillet. Stir until combined and warmed. Stir the tempered sour cream and the heavy cream into the mushroom mixture, then heat until warmed, about 5 minutes. Taste, and add salt if needed.

Step 6

Step 6 When the meatloaf is done, remove it from the oven, and allow to rest for 10 minutes. Slice the meatloaf into ½” slices. Cube the Chicken liver mousse into 3/8 inch dice and scatter it over the individual slices of meatloaf. Pour the Stroganoff mixture over the meatloaf and shower it with parsley. Serve immediately, perhaps with buttered egg noodles.