Chocolate Butter Fudge

2 cups granulated sugar
1 cup firmly packed brown sugar
1 envelope unflavored gelatine
1 cup milk
1/2 cup light Karo syrup
3 ounces Hershey's unsweetened baking chocolate
1 1/2 cups (3 sticks) unsalted butter
2 teaspoons vanilla extract
1 cup chopped pecans or walnuts

Line a 13 x 9-inch baking dish with wax paper.

In a large, heavy saucepan, combine the sugars and gelatine. Add milk, syrup, chocolate and butter.

Clip a candy thermometer to the side of the saucepan. Cook over moderate heat, stirring constantly. When the mixture reaches the soft-ball stage (238 degrees F), remove it from the heat. Pour into a large bowl and stir in the vanilla extract. Allow to cool for exactly 15 minutes.

Beat at high speed until the mixture begins to thicken. Stir in the nuts. Spread the fudge in the prepared pan and set aside to cool. Cut the fudge into squares and wrap tightly in plastic wrap. Store in an airtight container.