Line a 13-in. x 9-in. baking pan with foil and grease the foil with butter; set aside. In a large heavy saucepan, combine brown sugar and corn syrup. Cook and stir over medium heat until sugar is dissolved. Bring to a boil. Cook, without stirring, until a candy thermometer reads 300° (hard-crack stage).
Remove from the heat; stir in baking soda. Immediately pour into prepared pan. Do not spread candy. Cool.
Using foil, lift candy out of pan. Gently peel off foil; break candy into pieces. In a microwave, melt candy coating; stir until smooth. Dip candies in coating, allowing excess to drip off. Place on waxed paper; let stand until set. Store in an airtight container.