In a mixer with the paddle attachment, mix 8 tablespoons of the butter, flour, salt, and 2 tablespoons of the sugar until sandy. In a separate bowl, blend the egg yolk and the creme fraiche. Add the blended egg yolk and crème fraiche to the flour mixture and mix until barely combined. Form into a disk and chill. Meanwhile toss the sliced apples with 1/2 cup of the sugar and cinnamon.
Roll out the dough to a 1/8-inch thickness on a floured surface and cut out 8-inch disks or 1 large round disk and place on a parchment lined sheet pan.
Place the apples in the center of the dough, leaving a 2-inch flap of dough around the edge. Fold over the flap onto the apples, forming a rustic, uneven rim around the crostada. (The apples should NOT be completely covered with the dough.) Dot with the remaining 2 tablespoons of butter. Brush the edge with the cream and sprinkle with the remaining 2 tablespoons of sugar.
Bake in a preheated oven 350 for 25 to 35 minutes, until light golden brown and apples are tender. Let cool.
Yield: 1 large crostada or 4 to 6 individual servings