Crust: Combine flour, walnuts and brown sugar in bowl. Cut in 1/2 cup butter until fine. Press into bottom of greased 12x8x2-inch baking pan and bake at 400 degrees for 12 to 15 minutes. Cool.
Pineapple-Mint Filling: Drain juice from pineapple into saucepan. Bring juice just to boiling point. Dissolve lime gelatin in hot juice. Cool. Cream cream cheese with 1 cup sugar. Blend in gelatin mixture. Stir in pineapple. Chill until thick, but not set. Chill 2/3 cup evaporated milk with 1/8 teaspoon peppermint extract in small bowl until ice crystals form. Beat until thick. Fold into pineapple-cheese mixture. Spoon over baked crust. Refrigerate while preparing glaze.
Chocolate-Mint Glaze: Melt, stirring occasionally over low heat, chocolate chips and 1/3 cup evaporated milk. Add 1 tablespoon butter and 1/4 teaspoon peppermint extract.
Spoon glaze over filling; spread carefully. Chill at least 4 hours. Makes 12 servings.