For the dough: Cut butter into cubes, combine all ingredients and use fingers to blend until mixture resembles coarse meal (can use a pastry knife also).

Add 6 tbsp ice water, mix with fingers or large fork until dough just comes together.

Turn it out onto a well-floured board.

Form it into a disk with your hands and let sit for 15-30 minutes before rolling.

Boil ~4 cups (just enough to cover the apricots), add the sugar and apricots. Blanch for 90 seconds (up to 5 minutes), then drain and set aside to cool.

Blend together sour cream, 2 tbsp sugar, flour, salt, lemon juice, and vanilla.

Separately beat the 3 egg whites until stiff and fold into sour cream filling.

Then roll out and line 9" pie tin with dough and gently fill by layering apricots and filling.

Brush any remaining exposed crust with the egg yolk.

(Can make a top crust or lattice, if desired, by doubling dough recipe.).

Bake st 350 degrees Fahrenheit for 25-30 minutes.