Preheat oven to 375°F. Line a 9x13 baking pan with parchment paper leaving a overhand on two sides and grease lightly with cooking spray, set aside.

For the slab scone, in a large bowl, whisk together the flour, sugar, baking powder, salt and lemon zest. Add in the chilled butter and rub with your fingers or a pastry blender until the mixture resembles coarse crumbs of various sizes. Stir in the dried blueberries if using. Make a well in the center and add in the heavy cream and the 3 beaten eggs. Using a rubber spatula, mix until the dough just comes together. Switch to your hands towards the end to bring the dough together if need be.

Dump out into the prepared pan and pat the mixture out to an even layer. Beat the remaining egg with a splash of cream and whisk. Brush the scone with the egg wash and sprinkle with turbinado sugar. Bake until golden brown, about 20 to 25 minutes. Remove from the oven and set aside to cool completely in the pan.

Meanwhile, to make the topping, combine the blueberries, sugar, lemon juice and vanilla bean paste and set aside at room temperature for about 30 minutes, stirring ever now and then.

Beat the heavy cream with the powdered sugar, vanilla and salt on high until soft peaks form. Chill until ready to use.

Once the scone has cooled, lift out of the pan and set on a large platter. Top with the whipped cream, spreading out into an even layer. Then spoon the macerated blueberries on top before serving. Slice and enjoy!