Preheat oven to 350 degrees F. Cream butter and sugar. Beat in eggs. Dissolve soda in milk and add. Add vanilla. Fold in flour and salt slowly. Chill dough for half an hour. Roll to around 1/8 to 1/16-inch thick. Dip cookie cutter in flour before each cutting. Bake for 8 minutes. Cool and frost.
Blend butter and sugar. Add the vanilla and then the milk a little at a time until you have a stiff mixture to be used for decorating. To use as frosting, add a few more drops of milk and spread over cookie with a knife.