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1
: Assemble all the ingredients you will need for the caramel and place close to the saucepan you will be using. Place sugar in a large heavy sauce pan over medium high heat. Let the sugar begin to melt, then start to mix with a spoon. Mix occasionally until sugar has completely melted into a lightly golden color. Slowly and carefully pour in heavy cream-the sugar is going to immediately steam and harden into a lump. Turn the heat down to medium and continuously stir caramel until it is completely melted again and mixture is smooth, about 5 minutes. Stir in butter, vanilla, and salt, and mix until butter has melted completely. Take caramel off the heat and let come to almost room temperature.
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2
: In a large bowl, combine apples, sugar, lemon juice, cornstarch, cinnamon, and nutmeg, and stir to make sure it is well mixed. Let stand for 10 minutes.
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3
: Adjust oven rack to middle position and preheat oven to 375u00b0F. Line the baking dish with foil, then grease foil with butter.
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4
Put flour, sugar, baking powder, and salt in the bowl of a food processor. Pulse 5 times to combine. Add butter and pulse until it is cut to the size of peas. Add egg and heavy cream and pulse until mixture has the texture of wet sand and, when pressed between your fingers, holds its shape.
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5
Take 3/4 of the shortbread dough and press it into the prepared baking sheet. The bottom crust should be about 1/2-inch thick. Use a slotted spoon to remove apples from the bowl and spread evenly over top of shortbread. Cover the apples with the caramel sauce, gently reheating it over low heat if it's become too thick to spread. Use your fingers to form the remaining shortbread into crumbs and sprinkle the top with crumbs.
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6
Bake bars until top is golden and bubbling, about 50 minutes. Let cool completely before cutting.
