Bake oven to 350 F. Melt butter in microwave. Put flour in a medium bowl and add melted butter and mix well. Add chopped pecans in flour mixture and mix well. Put the pecan mixture in 9x13-inch baking dish and press down and spread the pecan mixture. Put the oven and bake for 20 minutes. Put the crust set aside and let it cool. Put the cream cheese, powdered sugar and cool whip in mixing bowl and mix together until blended well. In a large bowl, put chocolate pudding and milk and mix well until thickened. Add chocolate in cream cheese mixture and mix well until smooth. Put them on top of the crust and spread evenly. Add cool whip on top of chocolate. Refrigerate for two hours until firm and chill.