Following the directions will allow everything to come together at the end.
Place potatoes in a pot, cover with cold water and bring up to a boil. Season water with salt and boil potatoes until tender, 12 to15 minutes.
Heat a skillet with high sides over medium high heat. Add extra-virgin olive oil.
Add bacon. Crisp bacon and remove to paper towel lined plate.
Add sirloin to the pan and caramelize the meat, 7 to 8 minutes.
Add in the mushrooms and onions and cook until tender, 8 to 10 minutes more.
Then season with salt and pepper.
While meat cooks heat a small sauce pot over medium heat and melt butter, whisk the flour into butter, cook 2 minutes then whisk beef stock into flour, add Worcestershire and season sauce with salt and pepper, to taste. Thicken 6 to 7 minutes.
Turn on broiler and have top rack 6 inches away from broiler flame.
Pour gravy over meat and cook until the gravy thickens.
Put meat/mushroom/onion mixture into a 9 x 13 inch oven safe dish.
Place drained potatoes back into the pot you cooked them in to dry them out a little. Mash potatoes with egg yolk and sour cream.
Stir egg yolk into the potatoes.
Stir Ranch Dressing into the potatoes.
Stir shredded cheese into the potatoes.
Season the potatoes with salt and pepper and spread across the top of the meat in an even layer.
Garnish the potatoes with paprika.
Place under broiler to crisp and brown the potatoes, 2 to 3 minutes.