Created by ForeverMama on August 26, 2021
Step 1: Cook potatoes, in boiling salted water until tender, about 15 minutes; drain reserving 1/2 cup cooking water, if using in place of milk. Place cooked potatoes back into the same pot.
Step 2: While the potatoes are cooking, heat a large skillet over medium high heat. Add the bacon and cook until crisp. Remove the bacon with a slotted spoon and drain on paper towels; set aside. Add ground sirloin to hot bacon drippings and cook until browned, breaking up the larger pieces with a wooden spoon. Season the meat with salt and pepper. Add the onion and mushrooms. Cook, stirring occasionally, until tender, about 5 minutes. Sprinkle with the flour and cook, stirring constantly. for 1 minute. Stir the stock and Worcestershire sauce and cook until thickened, about 5 minutes. Taste and adjust seasoning with salt and pepper, if needed.
Step 3: Preheat oven to 400-degrees-Fahrenheit.
Step 4: Temper egg yolk by beating it with the reserved potato water or milk. Mash the potatoes with the egg yolk mixture sour cream and butter, then fold in the crumbled blue cheese and chives. Season the potatoes with salt and pepper, tasting for desired level of flavor.
Step 5: Spread the meat mixture in a 10-inch deep dish pie plate. Spread the potatoes over the meat mixture, in an even layer. Back for 20 minutes, Sprinkle the reserved bacon over the top and serve immediately while hot.