Step 1

Line a 3-quart rectangular baking dish with foil, extending foil over edges. Butter the foil; set aside. Place butter, brown sugar, corn syrup, condensed milk and 1/8 teaspoon salt in a large microwave-safe bowl. Microwave on 100% power (high) for 4 to 5 minutes or until butter is melted, stirring every minute. Microwave for 9 to 16 minutes more or until a candy thermometer inserted in center of mixture* registers 245° (firm-ball stage).** (In a 1000-watt microwave, begin checking temperature at 8 minutes; in a 850-watt microwave, start checking at 12 minutes.)

Step 2

When candy reaches firm-ball stage, stir in vanilla. Pour into prepared dish. Sprinkle top of caramel mixture with sea salt. Refrigerate 2 to 3 hours or until firm. To slice, use foil to lift caramel out of the dish. Cut into 100 pieces with a buttered knife. Wrap caramels in squares of waxed paper, twisting ends. Store at room temperature for up to 2 weeks.