Frosting:
Mix all ingredients, add the milk a little at a time until you reached the desired consistency. Add more milk for a thinner icing, more sugar for a thicker icing
Cookies:
1. Sift the flour, salt and baking powder
2. In another bowl, beat the butter until creamy, gradually add the sugar until the mixture is light and fluffy
3. Add the egg and vanilla and beat until well combined.
4. Gradually add the flour and beating until the mixture forms a dough.
5. Divide into two large logs.
6. Chill the dough until firm, at least 4 hours and up to 5 days.
7. Let the dough soften before cutting.
8. Preheat the oven at 375F and lightly butter the baking sheet.
9. Cut and shape at 1/8 inch thick and arrange about 1/2 an inch apart.
10. Bake until golden around the edges, around 10-12 mins.
11. Let it cool before piping the icing or storing.