In a small bowl, or onto a sheet of waxed paper, sift flour and baking powder together and set aside.

In a large mixing bowl, beat butter and sugar together on medium-high speed until light and fluffy, about 5 minutes.

Add eggs, vanilla and salt; mix on medium-high speed until well combined.

At low speed, add flour mixture in two batches, mixing just until incorporated.

Turn out the dough onto a clean work surface. Divide in half; pat into flattened rectangles and wrap each rectangle in plastic wrap. Chill for at least two hours or up to a week.

Preheat oven to 375 degrees F. Position racks at upper and lower thirds.

On a lightly floured surface, roll out one rectangle of dough to a thickness of 1/4 inch. Cut into desired shapes and, with a spatula, transfer shapes to parchment-lined baking sheets, about 2 inches apart. Chill in freezer or refrigerator until firm, about 15 minutes. Set scraps aside. Repeat process with second rectangle.

Gather up all of the scraps, roll out again. Chill for 15 minutes before cutting out shapes and adding to baking sheets.

If desired, decorate with colored sugar or sprinkles. Placing a baking sheet on each rack and rotating halfway through the baking time, bake until golden around the edges and firm to the touch (anywhere from 7 - 12 minutes, depending on your oven).

Transfer baked cookies to wire racks and allow to cool completely. Decorate with icing, if desired.

Cookies can be kept in an airtight container, layered between sheets of waxed or parchment paper, at room tempurature for up to three days.