In a large non-stick pan over medium high heat, melt half the butter until it sizzles. Add mushrooms and cook, stirring occasionally until reduced in size about ⅔.
Add shallots, garlic, tomato paste, herbs, salt and pepper. Continue to cook for 2-3 minutes until fragrant and shallots have softened.
Add white wine and cook down until wine has almost completely been absorbed.
Add remaining butter. Once melted, add flour and cook until mixture becomes quite thick and almost pasty. Cook for about 3 minutes.
Add beef stock in portions, ½ cup at a time. Once one portion of stock has been stirred in and has thickened, add the next portion. Once all the stock has been added, bring sauce up to a low simmer.
Transfer hot mushroom sauce to a blender, scraping out all chunks. Set pan aside. Blend until smooth and no large chunks remain. Using a mesh strainer, strain smooth mushroom sauce back into saucepan.
Over medium low heat bring sauce to a low simmer. Adjust seasoning to taste. If mixture is too thick, add more stock ¼ cup at a time until desired thickness is reached. If too thin, simmer sauce until it thickens on its own.
Meatloaf
Preheat oven to 350°F.
In the mixing bowl of an electric mixer, add all ingredients except beef. Mix on medium low speed for 3 minutes.
Add ground beef to mixture and continue mixing for about 1 minute until well blended.
Transfer meat mixture to a greased loaf tin. Pat down into corners of tin, then lightly lift tin and drop onto flat surface to remove any possible air bubbles that have formed in center.
Cover with foil. Bake for 60 minutes.
After 60 minutes, take meatloaf from oven and remove foil. Adjust heat of oven to 400°F. Carefully drain juices from tin into a separate container. (You can strain this, skim off fat and add the juice to your mushroom sauce!)
Spoon some of the mushroom sauce over top of the meatloaf just to coat surface. Return to oven for 10 more minutes. Repeat this step 2 more times so you’ve glazed the meatloaf 3 separate times with sauce.
Remove meatloaf from oven once internal temperature reaches 160°F. Loosely cover with foil and allow to rest for 25-30 minutes before serving.
Serve alongside mashed potatoes and your favourite steamed or roasted vegetables topped with remaining Mushroom Velouté.