For the pastry: Cream together the butter and sugar. Beat in the egg yolks. Quickly add the flour and mix just to incorporate. Wrap the dough in plastic and chill one hour. Roll out and line a 9-inch/23 cm-tart shell or ring. Wrap again and chill. Line the shell with foil, then pour in the beans right to the rim. Bake 20 minutes. Remove the beans and foil and return to the oven until lightly golden and completely cooked. Pull from the oven and paint the base with a little whisked egg white to seal the base.
For the filling: Cream the cheese with the sugar, then beat in the creme fraiche and vanilla. Spread the mixture in the base of the cooked shell once it has cooled.
Put 1 cup of the blueberries in a saucepan with 1/4 cup/60 ml water, the sugar, and the cornstarch. Bring to a boil and simmer until juicy and thick. Pour over the remaining berries in a bowl and toss to coat. Spread over the cream base and let set. Serve.