Cream butter and sugar until blended. Add eggs, one at a time, mixing well after each addition. Mix in vanilla extract.
Slowly add flour to creamed mixture and mix until blended.
In a separate bowl, mix flour and baking powder.
If the dough is too sticky, sprinkle a bit more flour.
Hand-roll teaspoon-sized balls and place 2" apart onto ungreased baking sheet.
Bake at 350 until cookies are set and bottoms are lightly browned.
Mix all ingredients with an electric mixer, or by hand. Beat until smooth.
Dip tops of cookies into frosting. Leave plain or add colored sprinkles. Let dry completely on cooling rack.