Preheat the oven to 400 degrees. On a lightly floured surface, roll out 1 piecrust into a 13-inch round. Trim 1 inch off two opposite sides, creating a shape with two straight sides and two round sides. Cutting parallel to the straight sides, cut the crust into 1/3-inch-wide strips. Arrange 3 strips of equal length next to each other and braid them; transfer to a baking sheet. Repeat with the remaining strips; cover and chill. Roll out the remaining piecrust to a 12-inch round; transfer to a 9-inch pie dish.
In a large bowl, toss the apples and lemon juice. In a small bowl, whisk 3/4 cup sugar, the flour, cinnamon, allspice and a pinch of salt. Toss with the apples.
Scrape the apple mixture into the dish, mounding in the center. Dot with the butter. Top with the braids, spacing evenly; trim any overhang. Fold the edges of the bottom crust over the ends of the braids; crimp the edges decoratively. In a small bowl, whisk the cream and yolk; brush on the braids. Sprinkle with the remaining 2 tbsp. sugar.
Bake the pie 30 minutes. Reduce the oven temperature to 350 degrees and continue baking until the filling bubbles, the apples are tender when pierced with a knife and the crust is browned, tenting with foil if browning too quickly, about 40 minutes more. Let cool to room temperature.