Heat oven to 350℉
In a medium mixing bowl, blend the butter and sugar together.
Add the eggs and the anisette liqueur. Mix until smooth.
Mix in the flour, baking powder, and salt.
Fold out onto a lightly-floured work surface and shape into two oblong loaves. The dough will be sticky. Lightly-flouring your hands will help with stickiness.
Bake on a parchment-lined baking sheet for 30 to 40 minutes. The biscotti loaf will become brown, cracked, and will sound slightly hollow when tapped. Remove and let cool for 10 minutes.
Increase oven temperature to 400℉.
Gently slice each biscotti loaf diagonally into 1/2-inch thick pieces. Lay each piece on the baking sheet with the cut side down.
Bake for 5 minutes.
Flip the biscotti.
Bake for 5 more minutes.
Cool and store in an air-tight container.