Preheat oven to 350 degrees

Butter and flour a loaf pan

Beat egg whites in a separate bowl until firm

In a second bowl, beat butter and sugar for 3 minutes, adding one egg yolk at a time while mixing well

Add whisky, mixing it in

Mix flour with baking powder and add to batter

Beat in 1/4 of the egg whites to form a smooth bater

Finally, slowly fold in remaining egg whites

Pour bater into prepared pan and sprinkle with sugar

place in oven for 40 to 45 minutes, use a toothpick to verify that is is baked

Remove from oven and allow to cool completely

Serve slices sprinkled with sugar