Dark Chocolate Crumb Bars

1 3/4 cups all-purpose flour
1/3 cup granulated sugar
1/4 teaspoon salt
1 2/3 cups (10-oz. pkg.) NESTLÉ® TOLL HOUSE® Dark Chocolate Morsels, divided
1 can (14 oz.)Sweetened Condensed Milk
1 teaspoon vanilla extract
1 cup chopped walnuts (optional)
Directions

PREHEAT oven to 350* F. Grease 13 x 9-inch baking pan.

BEAT butter in large mixer bowl until creamy. Beat in flour, sugar and salt until crumbly. With floured fingers, press 2 cups crumb mixture onto bottom of prepared baking pan; reserve remaining mixture.

BAKE for 10 to 12 minutes or until edges are golden brown.

COMBINE 1 cup morsels and sweetened condensed milk in small, heavy-duty saucepan. Warm over low heat, stirring until smooth. Stir in vanilla extract. Spread over hot crust.

STIR nuts and remaining 2/3 cup morsels into reserved crumb mixture; sprinkle over chocolate filling. Bake for 25 to 30 minutes or until center is set. Cool in pan on wire rack. Cut into bars.