In a bowl, whisk together apple cider and cornstarch.
In a large dutch oven, combine the apples, sugars, spices, apple cider, and cornstarch mixture over medium-high heat. Cook until the sauce has thickened and apples are tender about 20 minutes. Stirring occasionally. Mix in lemon juice and remove from heat.
While the mixture is cooling, preheat oven to 400 degrees F and position a rack at the lower third of the oven. Lay one pie crust at the bottom of the pan, ensuring the edge of the pie crust drapes slightly over the end of the cast iron.
When the filling has cooled a little, pour into the crust lined pan, and layer the top crust on top. Whether you do a lattice crust or a regular pie crust, brush with the milk and egg wash and sprinkle with coarse sugar.
Place in oven and bake for 1 hour. Remove, let cool for 1-2 hours until cool. Cut and serve.