This old fashioned peanut brittle recipe is made with real butter. It's the key to ace the crackly texture and rich flavor of this Christmas candy recipe. If any of your guests has a peanut allergy, swap in pecans or walnuts.
Line two large baking sheets with foil. Butter foil; set aside. Butter sides of a heavy 3-quart saucepan. In pan combine sugar, corn syrup, water, and butter. Cook and stir over medium-high heat until mixture boils. Clip a candy thermometer to side of pan. Reduce heat to medium-low; continue boiling at a moderate, steady rate, stirring occasionally, until the thermometer registers 275 degrees F, soft-crack stage (about 30 minutes). Stir in nuts; continue cooking over medium-low heat, stirring frequently, until thermometer registers 295 degrees F, hard crack stage (15 to 20 minutes more).
Remove pan from heat; remove thermometer. Quickly sprinkle baking soda over mixture, stirring constantly. Immediately pour onto prepared baking sheets. Cool completely; break into pieces. Store tightly covered up to 1 month. Makes 2-1/4 pounds (72 servings).