Start out by placing potatoes in a pot, cover with cold water, season with salt, and bring to a boil until tender. (HEADS UP: save about 1/4 cup of the starchy cooking water, just before draining the potatoes.)
Heat a skillet with high sides, over a medium-high heat. Add the bacon. Crisp the bacon and remove to a paper towel, lined plate. Next add the ground beef to your skillet, and brown the meat for about 5 minutes. Now add the mushrooms, and onions; cook until tender, and meat throughly browned. Add 2/3rds of the crispy bacon pieces. Season with salt and pepper.
While the meat cooks, heat a small saucepan, over medium heat, and melt the butter. Add the flour, and whisk together. Next, add the beef stock into the flour mixture. Add worcestershire, and season the sauce with salt, and pepper to taste. Let it thicken.
Next pour the gravy mixture, over the meat. Turn on your oven's broiler.
Now, drain the water off the boiled potatoes, and put the potatoes back into your pot. Temper the egg yolk by beating it with the starchy potato water that you reserved.
Pour into the pot with boiled potatoes; add the sour cream. Season with salt, and pepper; then mash your potatoes. Next, fold in the cheese, chives, and remaining bacon.
Using a 13" x 9" pan, layer your green beans; next add the meat, and gravy mixture.
Then spread on the layer of mashed potatoes. Sprinkle the top with paprika, and put in the oven to broil until the top becomes crisp, and brown.
We really love this recipe on a cold winters day. Please, free to tweak it to become your own ! Depending on what I have in my freezer, I sometimes substitute turkey burger which is also good, and less expensive. I have 'meat eaters' in the family so they want a lot of meat. You can cut back on the bacon if you like, and just put it into the potatoes. When possible, I'll make an extra, and put in the freezer for one of those days when I don't feel like cooking!
Hope you enjoy!