White Pecan Fudge

1 tablespoon plus 1/2 cup butter (no substitutes), divided
2-1/2 cups miniature marshmallows
2-1/4 cups sugar
1 cup whipping cream
16 squares (1 ounce each) white baking chocolate, cut into small pieces
2 teaspoons vanilla extract
2 cups chopped pecans

Line a 9-in. square pan with foil. Greased the foil with 1/2 tablespoon butter and set aside. Butter the sides of a large heavy saucepan with 1/2 tablespoon butter. Cut remaining butter into small pieces and place in a large heat-proof bowl; add marshmallows and set aside.

In the buttered saucepan, combine sugar and cream. Cook and stir over medium heat until mixture comes to a boil. Cover and cook for 2 minutes to dissolve any sugar crystals. Uncover; cook over medium heat, without stirring, until a candy thermometer reads 234 degrees (soft-ball stage).

Remove from the heat. Pour over butter and marshmallows; stir until melted. Add the chocolate. Continue stirring until chocolate and mixture is smooth. Stir in vanilla and nuts.

Pour into prepared pan. Refrigerate until firm. Lift out of pan; remove foil and cut into 1-in. squares. Store in an airtight container at room temperature. Makes about 3-1/2 pounds (about 6-1/2 dozen).