For the flaky butter pie crust: Mix the flour and salt in a large bowl. Add the butter and cut it in with a pastry blender until the largest pieces are the size of small peas and the mixture begins to clump on the pastry blender. Shuffle through the mixture with your hands, pinching chunks of fat to flatten them.
Stir the vinegar and 5 tablespoons ice water together in a bowl. Add the liquid to the flour mixture and stir with a fork. Pinch a clump of dough in your hands: If it feels moist and clumps together easily, it's probably hydrated enough. If it feels really crumbly, add another tablespoon or two of ice water until you can form a baseball-size clump of dough, packing it on as if you were making a snowball.
Divide the dough in half and form each half into a flat disk. Wrap both disks in plastic wrap and refrigerate for at least 1 hour and up to 2 days.
Thirty minutes before you're ready to roll out the dough, remove it from the refrigerator and let it sit at room temperature to soften. Preheat the oven to 375 degrees F.
For the blueberry filling: In a bowl, toss the blueberries with the sugar, cornstarch and lemon zest and juice and mix until combined.
Dust a worktop and rolling pin with flour. Roll out one dough disk a little less than 14 inch thick, about 14 inches in diameter. Fold the dough in half and transfer it to a 9- or 10-inch pie plate. Unfold. Press the dough into the corners, leaving the overhang for now. Refrigerate the first crust while you roll out the second disk of dough.
Remove the bottom crust from the refrigerator and fill it with the berry mixture. Tuck the pats of cold butter beneath the top layer of berries. Top with the second piece of dough, and trim both to a 1/2-inch overhang around the pie. Tuck the overhang into a roll and crimp the edge, pressing down to hook some of the dough over the edge of the dish, holding the pie. Cut a hole in the center of the pie, as well as some decorative vents.
Brush the top of the pie with cream and dust it with sugar. Bake for 20 minutes. Reduce the temperature to 350 degrees F and bake for another 20 minutes. Cover the edges of the pie with foil and continue to bake until the center juices bubble and thicken, 25 to 35 minutes more.
Let the pie cool until it is just warm to the touch before slicing and serving. Top with ice cream.