Grease the cookie sheet with the butter, and set it aside.
Decide on the amount of pecans you want to be candied, in terms of cups. Place the pecans into the large bowl.
Place the pot on a burner. Pour 1 to 2 cups of sugar into the pot for each cup of pecans. Pour water into the pot slowly until it barely covers the sugar.
Place ice water in the small bowl and set in the fridge to keep it cold.
Turn the burner on, and cook the sugar-and-water mixture until it reaches the "soft ball" stage, which is 235 to 240 degrees Fahrenheit. To test if the sugar has reached this stage, remove the small bowl of ice water from the fridge. Place a small amount of the melted sugar into it carefully with the wooden spoon, and see if it forms a soft ball.
Pour the sugar mixture over the bowl of pecans and stir constantly with the wooden spoon to coat the pecans completely with the melted sugar. Alternately, pour the pecans into the pan, stirring constantly and removing them from the pot before they cool completely.
Set the candied pecans on the greased tray. Roll the candied pecans in powdered sugar. Roll any broken up pieces of pecan into balls before rolling them in the powdered sugar.
Store the finished candied pecans in the airtight container.