In a medium saucepan, combine granulated sugar, white Karo syrup, and water over medium heat. Stir gently until the sugar dissolves completely, then increase the heat to boil until it reaches the soft ball stage (235°F–240°F).

While the syrup boils, place egg whites in a large mixing bowl. Beat the egg whites on medium speed until stiff peaks form (about 5-7 minutes).

Once the syrup reaches the desired temperature, slowly pour the hot syrup into the whipped egg whites in a steady stream, avoiding the beaters. Increase the mixer speed to high and whip until thickened and glossy sheen is gone (about 5-10 minutes).

Gently fold in the vanilla extract and then add the chopped pecans, mixing with a spatula.

Quickly drop spoonfuls of the mixture onto wax paper to form mounds. Allow to set at room temperature until firm (1-2 hours).