1. Refresh hashbrowns according to directions. Toss hashbrowns with eggs, flour, horseradish and 0.25 cups of the chives in a large mixing bowl until thoroughly combined.
2. In a separate bowl, stir together sour cream and remaining chives until thoroughly combined. Refrigerate until ready to use.
3. On a 400° F well-oiled grill, drop hashbrown mixture in 4-oz. portions using a #8 scoop and lightly press down to form 3-in. potato pancakes. Cook until golden brown, about 4 minutes per side. Top each pancake with a tablespoon of the sour cream mixture and serve.