The feta cheese cut into small cubes, pour hot water and leave to desalinated 3-4 hours. Drained. For caramel sugar, pour water and put to melt a light caramel without stirring. Add the butter, stir and pour heated cream. Stir until the mixture is homogeneous, then cooled. If left in the refrigerator, is compressed enough to be injected. Cookies are chopped in a food processor or grate. Add the butter and stir again. The resulting mixture is poured on the bottom of a baking dish or cake form, covered with baking paper. Pressed tightly with his hands over the entire surface. The coffee is dissolved in hot water. In a large bowl put the eggs, sugar, the feta cheese, coffee, sour cream and half the melted chocolate. All stir with wire or wooden spoon. Pour the mixture over the biscuit base. Top spray remaining chocolate and spread with a wooden skewer, to give a marble effect. Bake 40-50 minutes in an oven heated to 180 ° C without a fan. Cake is ready when the center rise. cooled cheesecake cut into squares and garnish with caramel.