Preheat oven to 180 degrees C.
Line a 23-25 cm spring form pan with a circle of baking paper. Grease well inside the pan.
In a small bowl combine flour and salt and set aside.
In a large bowl beat the egg yolks with the two kinds of sugar, whiskey and vanilla until thick. Wash the beaters and dry them with a towel.
In another bowl beat the egg whites for about 5 minutes, until thick.
Using a rubber spatula, gradually add the dry ingredients to the egg yolk mixture. Mix gently until absorbed. Carefully fold in the egg whites.
Pour the batter into the prepared pan and bake for 40-45 minutes or until a toothpick inserted in the center comes out clean. Remove the pan from the oven and let cool for 10 minutes. Transfer the cake to a wire rack to cool completely.