Beat the butter and sugar until light and white. Gradually add the egg, stirring well as you go. Stir in the ground almonds, whiskey, and flour. Sprinkle the pastry base with the toasted almonds and spread the filling over it, smoothing the surface with the back of a wet spoon. Pit and halve the fruit and arrange, cut side down, over the tart. Bake at 350 F for 35 to 40 minutes, until the filling is puffed up and golden. Cool, then top with glaze: Gently heat apricot jam and whiskey together until smooth. Brush a thin layer over the cooled tart. Serve with Irish coffee (recipe follows).