Core the apples then thinly slice about 1/8th inch (3mm).Tip: if it is going to be some time before you can use the apples place them in acidic water from lemon juice so that they don’t brown (oxidize).
Place the apples in a large bowl along with the sugar, brown sugar, 2 teaspoons of spice, salt, melted butter, and lemon juice. Toss thoroughly but delicately to combine.
Grease a 10-inch skillet with butter. Starting in the center of the skillet lay the coated apples in a spiral fashion, slightly overlapping each of the slices. Use any broken pieces to fill gaps. Continue until you have used all the slices of apple.
Over low heat, about 3/10, begin to cook the tart for around 35 minutes, slowly caramelizing the tart. It will take some time for it to start cooking but resist the urge to turn up the heat. After about 20 minutes you will see the apples begin to wilt and they will start to create a wonderful aroma.
Peel the butternut squash (pumpkin) and thinly slice about 1/8th inch (3mm).
Prepare a simple syrup in a small saucepan by combining the sugar and water over a gentle heat, then add 1 teaspoon of spice. Add the thinly sliced butternut and cook until it is just tender about 3 minutes. Remove the butternut and allow them to cool.
Preheat the camp oven to 410 degrees F (210 degrees C).
Once the apples have cooked down and are soft, about 35 minutes, arrange the butternut slices in layers over the top of the apples.
Place the puff pastry over the top of the butternut, and fold in any corners that overhang the skillet. Whisk the egg with 1 tablespoon of water then brush over the puff pastry.
Place the skillet in the preheated camp oven to cook for 15 minutes. The pastry will be puffed up and brown when ready.
Let the tart tatin cool then flip it out onto the serving tray, be careful of the hot syrup. Alternatively, cool the tart tatin completely by chilling overnight to allow everything to set. Then remove from the skillet, slice, and serve cold.