Step 1
Preheat the oven to 325 degrees F (165 degrees C).
Step 2
Melt butter in an oven-safe skillet over medium-high heat. Stir in mushrooms and a pinch of salt; cook and stir until mushrooms begin to brown about 5 minutes.
Step 3
Stir in fresh rosemary. Add flour and stir to coat the mushrooms; cook and stir for about 3 minutes.
Step 4
Whisk in beef broth 1/2 cup at a time whisking constantly to prevent lumps.
Step 5
Turn heat to high and bring the sauce to a simmer. Simmer a few minutes until sauce starts to thicken. Season with salt and pepper to taste.
Step 6
Remove from heat and stir in heavy cream.
Step 7
Slide prepared meatloaf into the sauce. Spoon sauce over the top of the meatloaf.
Step 8
Bake in the preheated oven until no longer pink in the center about 1 1/2 hours. An instant-read thermometer inserted into the center should read at least 160 degrees F (70 degrees C).
Step 9
Remove pan from the oven and gently remove meatloaf to a serving platter.
Step 9
Skim off any extra fat from the surface of the sauce.