I don't have vanilla flavored vodka or sour apple liqueur so I used plain NATO vodka and 3/4 oz fresh cold-pressed apple juice with 1/2 oz vanilla sugar syrup. I also used Canadian blended whiskey instead of bourbon to avoid overpowering the vodka and cut the lime back to 3/4 oz. Use a really big cocktail glass. Delightful tribute to Boris Pasternak.