1. Heat oven to 350°F.
2. Beat butter and brown sugar in large bowl until creamy. Add eggs, vanilla and instant coffee, if desired; beat well. Stir together oats, flour, baking soda, salt and 1 cup walnuts; gradually add to butter mixture, beating until well blended. (Batter will be stiff; stir in last part by hand.)
3. Remove 2 cups dough; set aside. Press remaining dough onto bottom of 15-1/2x10-1/2x1-inch jelly-roll pan. Prepare CHOCOLATE FILLING; spread over mixture in pan. Sprinkle reserved dough over filling. Sprinkle with remaining 1/2 cup walnuts.
4. Bake 25 minutes or until top is golden. (Chocolate will be soft). Cool completely in pan on wire rack. Cut into bars. About 4 dozen bars.
1 tablespoon butter or margarine
7 sections (1/2 oz. each) HERSHEY'S Unsweetened Chocolate Baking Bar, broken into pieces
1/2 cup sugar
1 can (14 oz.) sweetened condensed milk (not evaporated milk)
1-1/2 teaspoons vanilla extract
Melt butter in medium saucepan over low heat. Add chocolate; cook and stir until smooth and completely melted. Stir in sugar and sweetened condensed milk. Cook, stirring constantly, until mixture thickens and sugar is dissolved. Remove from heat. Stir in vanilla.
MICROWAVE DIRECTIONS: Place butter and chocolate in microwave-safe bowl. Microwave at HIGH (100%) 1 to 1-1/2 minutes or until chocolate is melted and mixture is smooth when stirred. Stir in sweetened condensed milk and sugar. MIcrowave at HIGH 3 to 4 minutes, stirring every minute, until mixture thickens and sugar is dissolved. Stir in vanilla.