Heat oven to 375 degrees. Cook bacon, drain on paper towels. Slice your potatoes, chop your bacon, and grate your cheese. Roll one of your dough disks out, and place in a 9 inch deep dish pie plate. Cover it with plastic wrap and place it back in the fridge. In a small saucepan, combine half & half, thyme, salt & pepper and corn starch. Whisk together. Over medium low heat, bring to a gentle simmer. Simmer 5 minutes, stirring continually. Remove from heat. Layer 1/2 of the potatoes in your pie dish. Top with half of the bacon, and then half of the cheese. Repeat with remaining potatoes, bacon and cheese. Pour the cream mixture over the top of the filling.
Roll out your second dough disk, and cover the filling. Roll and pinch together the two dough layers. Whisk together the egg yolk and water. Brush all over the top of the crust.
Cut a 2 inch slit in the center with a sharp knife. Bake 1 hour, 10 minutes.