Root Beer Fudge

1 cup butter
1 1/3 cups milk
4 cups granulated sugar
2 1/2 teaspoons root beer extract
1/8 teaspoon salt
1/4 cup chopped pecans (optional)

In a saucepan, melt butter over low heat and then add remaining ingredients. Place over medium heat and cook until the mixture reaches a boil, stirring constantly. Carefully clip a candy thermometer to the side of the pan. Continue to cook, stirring constantly, until the mixture reaches the softball stage (234 degrees F), about 20 minutes. Remove from heat and beat until thick. Transfer immediately to well-greased 9-inch square glass dish and sprinkle with chopped pecans. Cool thoroughly before cutting.