- Cream butter and sugar in the bowl of an electric mixer on medium speed. 
- Add in the egg and vanilla. 
- In a separate bowl, combine the flour and salt, then stir into the butter mixture with the mixer on low. 
- Cover dough with plastic wrap and refrigerate for 30 minutes. 
- Preheat oven to 350 degrees. 
- Line a cookie sheet with a silpat mat or parchment paper. 
- On a floured surface, roll out the dough to a 1/4 inch thickness and cut into your desired shapes with cookie cutters. 
- Place the cookies on the prepared pan and bake for 8-10 minutes, until the edges are starting to turn golden, but not brown. 
- These cookies are supposed to not look done when you take them out, but they should be firm and set. 
- They will have a soft texture when cooled if they do not bake too long. 
- Transfer to a wire rack and cool while you prepare the icing. 
- To make the icing, sift the sugar into a bowl, add the milk and food coloring (if using) and stir. 
- If mixture is too thick, add a little more milk. 
- If mixture is too thin, add a little more sugar. 
- This is simple to adjust to get the right consistency. 
- Spread icing on cookies when they are completely cooled. The icing will set when they are completely dry.