Line a baking sheet or 15- x 10-inch jellyroll pan with aluminum foil; grease foil with butter. Set pan aside.
Melt 3 tablespoons butter in a small skillet over medium heat. Add almonds, and cook, stirring constantly, 2 minutes. Remove from heat.
Cook sugar and 1/4 cup water in a small heavy saucepan over medium-high heat, stirring constantly, until mixture starts to boil. (Use a small brush dipped in cold water to brush down sugar crystals that cling to sides of pan.) Boil without stirring about 10 minutes or until a candy thermometer reaches 310° (hard-crack stage). (Mixture should be golden.) Remove from heat, and stir in almond mixture and baking soda.
Pour mixture immediately onto prepared baking sheet, spreading mixture quickly into an even layer with a metal spatula. Allow to stand 30 minutes or until hardened. Break into pieces.