Line baking sheet with foil. Butter foil; set aside.
In a heavy 8-inch skillet, combine almonds, sugar and butter. Cook over medium heat, carefully stirring constantly for about 9 minutes or until the sugar melts and turns a rich brown color (mixture may splatter).
Remove from heat. Immediately stir in vanilla. Spread the nuts on prepared baking sheet. Cool completely.
Break into clusters. Makes about 2-3/4 cups.
Prepare the glazed nuts. Store in a covered container at room temperature for up to 2 weeks.