Split your pie crust into two equal parts. Roll out one half out into a 10-12 inch circle and place into your pie plate. Trim the edges. Preheat your oven to 450 degrees.
Stir together your apples, lemon juice, heavy cream, vanilla, brown sugar, 1/2 cup sugar, 1/2 cup flour, cinnamon, nutmeg, and salt in a large bowl.
Melt four tablespoons of butter in a medium sauce pan. Add your apple mixture and cook for 10 minutes, or until your apples are softened. Pour into your prepared shell.
While your apples are cooking, stir together 3 tablespoons of sugar and 1/4 cup of flour. Melt the remaining two tablespoons of butter and mix into your flour. Stir in the toffee bits and sprinkle evenly over your pie.
Roll out your top crust and place over your pie. Cut slits for ventilation, brush with an egg wash, and sprinkle with sugar.
Bake your pie for ten minutes. Reduce the heat to 350 degrees and continue baking for 40 minutes, or until golden.