Use 1 tablespoon of the butter to grease a 13" x 18" non-stick baking sheet and set aside. Place the sugar, corn syrup, water and vanilla in a tall, narrow pot (about 5 to 6 inches wide; and 6 to 8 inches tall). Bring to a simmer over medium to medium-high heat, stirring occasionally to dissolve the sugar. Attach a candy thermometer to the side of the pot and continue simmering until the syrup reaches 250°F. Stir in the nuts and salt and continue simmering until the temperature reaches 290 degrees F. Remove from heat and carefully stir in the remaining 2 Tbsp. butter and baking soda. Pour onto the baking sheet and very quickly spread with a heatproof spatula. When the brittle is set, but still warm, flexible, and safe enough to handle, use a thin spatula to loosen and lift the brittle from the bottom of the pan. Allow the brittle to cool to room temperature. Cover until ready to break into delicious bites.