Prepare the crust first: into a food processor, add the flour, sugar, salt and butter. Pulse mixture until butter is broken down into small crumbs. Slowly add the water and pulse until dough comes together into a ball. Turn dough out onto a floured work surface and knead just until dough is smooth. Cover dough with plastic wrap and refrigerate for 1 hour.

Meanwhile, prepare the fillings. Place softened cream cheese into mixer bowl and whisk on high speed for several minutes until light and fluffy. Add the lemon juice, lemon zest and confectioner's sugar; whisk until smooth.

In a small bowl, toss together the blackberries with 1/2 cup sugar and 2 tablespoons cornstarch; set aside.

Roll out chilled dough on floured work surface into a large circle, large enough to have 2-3 inches of hang over. If using a spring form pan, line it with parchment paper; or use a regular pie dish. Transfer dough into pan and leave extra dough around edges.

Fill pie with cream cheese mixture, followed by blackberries. Fold dough over the edges to create a rough edge. Brush the top of the crust with beaten egg and sprinkle with sugar crystals.

Bake in oven preheated to 350F until edges are golden brown; mine was in the oven for 1 1/2 hours. Remove pie from oven and let it cool at room temperature for 3-4 hours, then refrigerate if not serving. Serve with vanilla ice cream or whipped cream.