1 egg yolk, whisked with a splash of water
(she added 1/4 tsp dried thyme but I didn't have any so I just skipped it and it was still really flavorful!)
Preheat oven to 375 degrees. Cook the bacon til crispy. Slice potatoes in half lengthwise then slice them to make half moons. Put pie crust into your pie pan and working in circles put a layer of potatoes down to cover the bottom. Sprinkle with salt and pepper, then crumble one piece of bacon. Repeat 3 more times. The pan should be nearly full. Top with the shredded cheese. If you have thyme whisk it with the cream. Slowly pour cream over the entire pie and let it seep down between the potatoes.
Cover the pie with your second crust and crimp the edges closed. Brush with the edges and top with egg wash. make some slits on the top so the steam can escape. Place on a baking sheet and bake until the edges are browned and crispy and the potatoes are cooked through. It'll be about 50-60 minutes. If the edges get too brown cover them with tin foil. Take the pie out when done and let it sit 15 minutes before serving.