Preheat the oven to 375 degrees F. Line a baking sheet with parchment paper. Place the flour, baking powder, sugar, salt and currants in a bowl and stir to combine. Cut in the butter until the mixture is a pea-sized crumble. Add 1 cup of the eggnog and very gently stir until the dough just holds together. Transfer the dough to a lightly floured surface and very gently shape into a ball. Gently press the dough into a circle that is about 1" thick. With a 3" round cookie cutter, cut the dough into 10 to 12 rounds and place on the baking sheet. Brush the tops of the scones with the remaining 2 tablespoons of eggnog. Bake for 18 to 20 minutes, or until puffed and golden. If desired, broil the tops of the scones for a few seconds to enrich their colour.