Lightly grease three baking trays.
Cream the butter with the icing sugar until very soft, light and fluffy.
Beat in the egg yolk and milk.
Sift together the flour and baking powder, then gradually work these dry ingredients into the creamed mixture, together with the chopped almonds.
Divide the dough into 40, and form each piece into an 8 cm/ 3 1/2 in long roll, tapering off at each end.
Arrange each roll in the form of a cresent on the baking trays.
Bake the crescents in a moderate oven (180 C, 350 F, gas 4) for 15-20 minutes, or until lightly browned.
Immediately they are removed from the oven, brush the crescents with rosewater and sprinkle them with icing sugar.
Remove the hot biscuits from the trays and transfer them to a wire rack to cool completely.
Variation Brandy crescents: make up the dough as for rosewater crescents, replacing the milk with 1 tablespoon brandy.
When they are removed from the oven, brush the crescents with brandy instead of rosewater, otherwise follow the method for making rosewater crescents.