Grease a 13 x 18-inch sheet pan (with 1-inch or higher sides) and set aside.
With a knife or a food processor, chop the toasted walnuts until very fine and no large chunks remain.
In a shallow dish, mix finely chopped walnuts, brown sugar, and cinnamon until fully incorporated. Set aside.
In a separate small bowl, mix together 1/2 cup of the date caramel and raisins. Set aside.
On a lightly floured surface, roll out pie dough and cut into 8 x 8 inch squares. Cut the remaining dough into decorative pieces, like leaves, using cookie cutters if desired. Set aside.
Peel and core apples.
Working one at a time, roll the outside of each apple in the brown sugar-cinnamon walnut mixture until evenly coated. Set the apple in the middle of a pie dough square, on a lightly floured work surface, with the cored hole facing up. Use a small spoon to fill the hole in each apple with the date/caramel/raisin mixture.
Working with slightly wet fingers, pull each corner of the pie dough to the top of the apple and gently press them together. Then gently fold the dough to the right, down the seams and press it into itself. Repeat this around the whole apple to make a sort of beggar’s purse. Pinch each seam with slightly damp fingers to fully enclose the pastry around the sides of the apple. Add any decorative pie dough elements to the dumpling.
Place each dumpling on the greased sheet pan. Place in the refrigerator for at least 1 hour, or overnight, to chill.
When ready to bake, preheat the oven to 400℉ (204℃).
Meanwhile, in a small pot combine the apple cider vinegar, sugar, butter, and vanilla/date balsamic vinegar over medium-high heat and stir until sugar is dissolved (about 5 minutes). Carefully pour this liquid over the chilled dumplings and onto the pan.
Bake in a preheated oven until golden brown and crispy, about 50-60 minutes. When there are 20 minutes of cook time remaining, combine the beaten egg and water in a small bowl and whisk well to combine. Brush the top of each dumpling with egg wash, then finish baking.
Using a spatula or large spoon, spread a few tablespoons of date caramel on a dessert plate or in a shallow bowl. Place a baked dumpling on top of the caramel and serve with a tablespoon or so of the pan sauce drizzled over the top - and vanilla ice cream!