2 lbs. Idaho potatoes, peeled & cut into chunks
1/2 Tbsp extra-virgin olive oil
4 slices bacon or peppered bacon, chopped
2 lbs. ground sirloin
1 onion, chopped
1/2 lb. button mushrooms, quartered
2 Tbsp. butter
2 Tbsp. all-purpose flour
1 1/2 cups beef stock
2 Tbsp. Worcestershire sauce
1 egg yolk
3 Tbsp. sour cream
1/2 lb. blue cheese, crumbled
3 to 4 Tbsp. chives
1 tsp paprika
Place potatoes in a pot, cover with cold water and bring to a boil. Season water with salt and boil until tender, 12 to 15 minutes. Heads up: save a ladle of starchy cooking water just before draining.
Heat a skillet with high sides over medium high heat. Add olive oil, half a turn of the pan and the bacon. Crisp bacon and remove to a paper towel line plate. Add sirloin to the pan and caramelize the meat, 4 to 5 minutes. Add in the mushrooms and onions and cook until tender, 6 to 7 minutes more; then season with salt and pepper.
While the meat cooks, heat a small sauce pot over medium heat and melt butter. Whisk the flour into the butter; cook 2 minutes. Whisk beef stock into flour, add Worcestershire and season sauce with salt and pepper, to taste. Thicken 6 to 7 minutes.
Pour gravy over meat and turn on boiler.
Temper egg yolk by beating it with the starchy potato cooking water. Place drained potatoes back into pot you cooked them in to dry them out a little. Mash the potatoes with egg yolk and sour cream. Fold in crumbled blue cheese and chives. Season the potatoes with salt and pepper.
Unless the pan you used to prepare your meat mixture in is oven safe, transfer your meat mixture to an oven safe dish. Spread potatoes across the top of the meat in an even layer. Garnish the potatoes with paprika and place under broiler to crisp and brown the potatoes, 2 to 3 minutes. Crumble reserved bacon over top. Serve immediately right from the hot skillet or dish.
*Adapted from Rachel Ray