Preheat oven to 450º F.
Prepare your pie crust in a 10 inch pie plate and butter or spray one additional ramekin.
Mix together all liquid ingredients in one bowl and whisk together the dry ingredients in another. Slowly pour the dry ingredients in to the liquid bowl while stirring. Beat until totally combined.
Pour into prepared pie plate, leaving at least 1/4 inch between the batter and the top of the pie crust. Pour any remaining batter into prepared ramekin(s). Smooth the top of the pie with a rubber spatula.
Brush crust with egg wash (full egg, mixed + 1 Tbs. water) or milk or oil (to help the crust brown), then cover with pie crust covers for at least the first 30 minutes of baking -- longer if you're using decorative pie crust cut-outs like some I've pictured here which are quite thin and delicate, and therefore would be prone to over-cooking/burning if not covered.
Bake at 450º F for 15 minutes, then reduce heat to 375º F and bake for 15 more minutes.
Remove pie crust covers and brush the crust edges with egg wash, milk or oil again, then bake another 15 minutes, or until a knife inserted into the pie comes out clean. The middle should still be slightly jiggly, not totally firm. (~45 minutes total bake time)
Turn off the oven but leave the pie inside the oven with the door cracked open so that the pie cools slowly for 20 minutes more; this will help prevent the custard from cracking and minimize shrinking.