ALL BUTTER CRUST: In a large bowl, whisk together the flour, sugar and salt; set aside.
Using the large holes of a box grater, quickly grate the frozen butter. Add the butter to the flour mixture. Using a pastry blender, quickly work the butter into the flour until the mixture resembles small peas.
Using a wood spoon, stir a 1/2 cup of ice cold water into the butter/flour mixture until incorporated. Press the dough between your fingers, if it sticks together it’s ready. Add more water if necessary, a tablespoon at a time, up to 3 tablespoons if needed.
Pour the dough out onto a lightly floured surface. Knead the dough a couple of times to form a ball. Divide the ball in half, flatten each half into a disc, then wrap each disc in plastic wrap. Refrigerate for at least 1-2 hours before using. (Freeze extra dough disc for up to a month; thaw in the refrigerator before using.)
Remove 1 dough disc from the refrigerator. On a lightly floured surface, roll the disc into a circle, large enough to fit a 9-inch deep dish pie plate. Transfer pastry to the pie plate; cut the edges leaving a 1/2-inch overhang. Tuck the overhang under to make a nice rolled edge around the pie, and then flute the edges to make a decorative edge. Prick the bottom and sides with a fork. Place the pie plate in the refrigerator while you work on the filling.
SOUR CREAM FILLING: In a medium bowl, whisk together the sugar and flour. Add sour cream, eggs and vanilla extract; whisk until combined.
Remove the pie plate from the refrigerator. Pour the raspberries into the bottom of the pastry. Pour the filling evenly over the raspberries.
CRUMB TOPPING: In a medium bowl, whisk the flour, sugar, brown sugar, cinnamon and nutmeg until combined. Pour the melted butter into the bowl stir until a crumble forms.
Sprinkle the crumb topping over the pie.
EGG WASH: In a small bowl or cup, whisk together 1 egg and 1 tablespoon of water; lightly brush over the edges of the crust. (Note: you won’t use all of the egg wash.)
Bake the pie at 350 degrees for 1 hour and 10 minutes. If the crust starts to brown too quickly, cover the pie with aluminum foil for the remaining baking time. The pie is done when the filling is somewhat firm.
Let the pie cool for at least 1 hour on a cooling rack. Transfer the pie to the refrigerator for several hours before cutting into slices. Serve with whipped cream if desired.