Soften butter either by leaving it on the table for a few hours or using the defrost setting on your microwave. With a fork, blend butter, sugar, and coriander until fully combined. Work in baking powder and then flour, a little at a time, until fully combined, then add milk and amaretto. This should give a medium-density, relatively brittle dough.Roll the dough into a cylinder, wrap it in plastic wrap, and leave it in the freezer for 20 minutes, while you preheat the oven to 350F/180C. Slice the roll into discs about 1/4″ thick and lay them on a greased baking sheet. Press an almond into the centre of each. Bake for 9m, then paint with melted butter and coriander, and bake another 8m. Biccies should be brown around the edges when you take them out. Let cool for at least 5m before serving.