In a mixing bowl, whisk together flour, baking powder and salt. Set aside.

In the bowl of a standing mixer, beat the butter on medium-high until smooth. Add sugar and beat on high until light and fluffy, ~2 minutes.

Add eggs one at a time, mixing between each addition. Add vanilla and mix for 1 minute more.

Add dry ingredients in three increments, mixing between each one.

Divide dough into three even portions.

Working with one portion of dough at a time, roll each into a 11" x 11" square. (I use a permanent marker to draw a square on a piece of wax paper and use that as a guide.)

Refrigerate dough for 30 minutes until chilled.

Remove dough from refrigerator and stack the three portions (in any order). Gently press layers together.

Using the bottom sheet of wax paper to lift dough, roll it into a log. Press gently as you roll to avoid gaps. Wrap the dough tightly in wax paper and then in foil.

Refrigerate for 2 hours or up to 5 days. (At this point the dough can be frozen for up to 3 months; defrost in the refrigerator for 2 to 3 hours before baking.)

Preheat oven to 375 degrees F.

Using a sharp knife cut roll into ⅛" slices. Place slices on an ungreased baking sheet. The cookies will spread as they bake, so leave 2" between.

Bake until cookies appear just set in the middle, 8 to 10 minutes. (The texture will be tender and buttery. I've also been known to bake these for as little as 6 minutes. Soft, gooey, delicious.) Transfer to a cooling rack and allow to cool completely.

Store in an airtight container for up to 3 days.