Butter two baking sheets and set aside.

Combine sugar, corn syrup, and water in a 3-cup saucepan. Bring to a full boil over medium heat, stirring occasionally, until sugar is dissolved (about 15 minutes). Add butter; continue heating over medium heat, stirring occasionally, until mixture reaches soft crack level (280°F - about 40 minutes).

Add nuts; continue heating over medium heat stirring constantly until mixture reaches hard crack level (305°F -- about 20 minutes).

Remove from heat. Add baking soda and stir briskly until thoroughly blended. Pour onto two buttered baking sheets. With back of spoon, spread about 1/4" thick (i.e., about the thickness of the nuts). Cool until hard, then crack into pieces.

Variation: Chocolate Brittle

For Chocolate Brittle (great with peanuts!), when adding the butter, also stir in the 1/2 cup of cocoa; then, just before adding nuts, thoroughly stir in the teaspoon of vanilla.