Mix the flour, salt, and sugar together in a large bowl. Add the butter. Using a pastry cutter or two forks, cut the butter into the mixture until it resembles coarse meal (pea-sized bits with a few larger bits of fat is OK). A pastry cutter makes this step very easy and quick. Drizzle the cold water in, 1 Tablespoon (15ml) at a time, and stir with a silicone spatula or wooden spoon after every Tablespoon (15ml) added. Do not add any more water than you need to. Stop adding water when the dough begins to form large clumps. I always use about 3/4 cup (180ml) water. Transfer the pie dough to a floured work surface. Using floured hands, fold the dough into itself until the flour is fully incorporated into the butter pieces. The dough should come together easily and should not feel overly sticky. Form dough into a ball. Divide dough in half. Flatten each half into 1-inch thick discs using your hands. Wrap each tightly in plastic wrap. Refrigerate for at least 2 hours (and up to 5 days) or freeze for up to 3 months. Thaw overnight in the fridge before using.

Mix all of the filling ingredients together in a large bowl. Set aside.

Preheat oven to 375°F (190°C).

Remove 1 disc of pie dough from the refrigerator.Keep the other in the refrigerator as you work. On a lightly floured work surface, roll the dough out into (roughly) an 18×13-inch rectangle. Make sure to turn the dough about a quarter turn after every few rolls. Carefully place the dough into a 10×15-inch jelly roll pan; there will be overhang on the sides—trim it to be about 1 inch. Smooth the crust out so it fits nicely into all the corners of the pan.

Spread filling evenly on top of crust.

Roll out the 2nd pie dough disc in the same manner and size as the first. Drape over filling and fold the bottom crust’s overhang over the edges. Seal them shut with your fingers and crimp the pie crust edges with a fork. Cut slits into the top of the crust, then brush with a thin coating of egg wash. Sprinkle with coarse sugar.

Bake the slab pie for about 40-46 minutes until the crust is golden brown and you can see the filling bubbling. Remove from the oven and allow to cool on top of a wire rack for a few hours. You can serve this pie a little warm or at room temperature (or cold!).

Before serving, whisk all of the glaze ingredients together and drizzle over pie. Cut into slices and serve. Cover leftovers tightly and store in the refrigerator for up to 3-4 days.