- *Spoon & Sweep method: Use a spoon to fill measuring cup with flour until required amount is obtained. Scooping measuring cup directly into flour bag will firmly pack flour resulting in too much flour required for recipe.
- If grapes are large, cut in half and then measure to obtain 6 cups. When weighing grapes this step is not necessary.
- Place grapes (unpeeled) in a food processor and pulse until grapes are about in 5-6 pieces. Do not worry if some parts are smaller and some are larger.
- Place rather soupy mixture into a saucepan. Add sugar, salt, and flour. Do not add cornstarch yet.
- Whisk together to a boil. Remove from heat and add butter. Set pan in an ice bath to cool.
- Roll half of dough on a lightly floured surface into a circle and until it is large enough to cover a 9-inch pie pan. Keep remaining dough in refrigerator.
- Cut away excess dough from sides and set on an aluminum foil-lined cookie tray for easy cleaning after baking.
- Preheat oven to 350°F.
- Once grape filling has cooled to room temperature, whisk in cornstarch and pour filling into pie shell.
- Roll remaining dough about 3 credit cards thick and slightly wider than the pie. Using a cookie cutter cut about 8 vent holes into pie dough.
- Brush a very thin film of water on edge of pie crust. Place rolled pie dough onto pie. Press to seal edges. Using a knife, make small cuts on edge of pie.
- Brush pie with a thin layer of water (do not use egg wash) and sprinkle evenly with about 1 tablespoon of granulated sugar.
- Place in oven and bake pie for about 75 minutes. Thick bubbles (consistency of honey) should be visibly showing through vent holes. If the crust gets too dark during baking, cover loosely with aluminum foil.
- Before serving place a small round plate on center of pie and sprinkle outer edge with powdered sugar (optional).