1. In a large bowl, beat butter and sugar until creamy and smooth.
2. Add vanilla extract and beat well.
3. Add flour in 2 parts, and then the ground pecans. Mix just until smooth. I use a spatula. 
4. Gather into a ball, cover in plastic wrap and chill or refrigerate for at least 3 hours.
5. Preheat oven to 350ºF/180°C.
6. Line a cookie sheet with parchment paper.
7. Roll portions of cold dough between your palms to form balls.
8. Place 1 inch apart on the lined baking sheet and flatten them slightly.
9. Bake for 15-18 minutes, depending on the thickness until they are a bit golden and slightly cracked. 
10. Let cool on a wire rack.
11. Roll in confectioners' (powdered) sugar to coat. Don't skip this step, as it adds an extra sweetness that is needed, as pecans can have a bitter tone sometimes. 
12. These cookies freeze well unbaked. When you need them, line them up on a parchment-lined or greased baking tray, thaw, and bake.

Test run: I always recommend baking a couple of cookies first to check the temperature and baking time. All ovens are different, and the dough's temperature is also a variable, so you might need more or less time.