Grease a 15x10x1-in. pan with 2 teaspoons butter; set aside.
In a 2-qt. microwave-safe glass dish, combine sugar and corn syrup. Microwave, uncovered, on high for 4 minutes or until a candy thermometer reads 238° (soft-ball stage).
Add pecans. Microwave for 4 minutes or until a candy thermometer reads 300° (hard-crack stage). Mixture will be very hot. Vigorously stir in the baking soda, vanilla and remaining butter until blended.
Quickly pour into prepared pan; spread with a metal spatula as thin as possible. Cool completely; break into pieces. Store in an airtight container with waxed paper between layers.
Editor’s Note: We recommend that you test your candy thermometer before each use by bringing water to a boil; the thermometer should read 212°. Adjust your recipe temperature up or down based on your test.