PREHEAT oven to 350°F. Line 15x10x1-inch baking pan with foil; grease foil. Beat butter, flour and 1/2 cup of the sugar in large bowl with electric mixer on medium speed until mixture resembles coarse crumbs. Press firmly onto bottom of prepared pan. Bake 10 min. or until lightly browned.
MICROWAVE corn syrup and chocolate in large microwaveable bowl on HIGH 2 to 3 min. or until chocolate is almost melted, stirring after 1-1/2 min. Stir until chocolate is completely melted. Add remaining 1-1/2 cups sugar and eggs; mix well. Stir in peanuts and raisins. Pour over crust; spread to evenly cover crust.
BAKE 25 to 30 min. or until filling is firm around the edges and slightly soft in center. Cool completely in pan on wire rack. Cut into 48 bars.
RECIPE COURTESY OF KRAFT FOODS