Combine flour and sugars. Cut in butter until crumbly. Stir in nuts Reserving 1 1/2 cups crumb mixture. Press remaining crumb mixture into bottom and half way up sides of 13 x 9 x 2 inch lightly greased baking dish. Spoon mincemeat over crust.
Combine pumpkin, sweetened condensed milk, eggs, cinnamon, nutmeg and salt. Mix well. Pour over mincemeat layer, top with reserved crumb mixture. Bake 15 minutes. Reduce oven to 350º Bake 40-45 minutes longer or until golden brown around edges. Cool. Cut into squares.
Serve warm or at room temperature. Store leftovers covered in refrigerator.