In the mixing bowl of a stand mixer, using the whisk attachment, add the butter, sugar, vanilla, egg, and blend until light and fluffy.
Switch to the paddle attachment. Add the chopped pecans, and blend lightly.
In a separate bowl, add the flour, and baking powder, and stir well to blend. Add the flour a little at a time and mix on low to blend, until all the flour is added. Continue to blend the cookie dough until it's completely blended and a smooth ball starts to form. Scrape down the mixing bowl as needed.
Line two cookie sheets with parchment paper, and roll the cookie dough into small balls, about 1 inch balls, and place the balls on the parchment paper.
Bake at 350 degrees for about 15 minutes, or just until the cookies start to turn a light golden brown around the edges.
About halfway through baking the cookies, check the oven, and the cookies may have started to crack a little. Take a flat bottom glass, dip it in sugar before lightly applying to each cookie - smash the cookies very gently, and slightly, making them a little flatter, and spread out a little more. This will give the cookies the crinkle look.
When the cookies are done, remove from the oven to a wire rack to cool completely. While cookies are cooling, make the frosting.