In a mixing bowl, cream together the butter and sugar until light and fluffy.
Add the eggs one at a time, beating well after each addition. Stir in the vanilla extract.
In another bowl, whisk together the flour, baking powder, and salt. Gradually add to the creamed mixture alternately with the milk, beating well after each addition.
Pour the batter into a greased and floured baking sheet. Bake for 15 minutes or until a toothpick inserted into the center comes out clean.
Let the cake cool on a wire rack. Once cooled, cut into small squares or use a cookie cutter to make shapes.