Crust and topping:
Filling:
Preheat oven to 375 degrees F and grease a 9 by 13 inch pan with butter.
In a medium bowl, stir together the oats, brown sugar, salt, cinnamon, and flour. Cut in the butter until it resembles coarse crumbs. Gather into a ball and divide mixture, reserving one third.
Press two thirds of mixture evenly in the bottom of the baking pan, coming 1 inch up the sides.
Bake 15 minutes.
To make the filling, combine the pumpkin, eggs, molasses, evaporated milk, sugar, flour, salt, vanilla, cinnamon, ginger, and cardamom in a medium bowl. Whisk until smooth. Pour over partially baked crust. Smooth the filling. Bake 20 minutes and remove from the oven.
Crumble the remaining crust mixture, distributing it evenly on top of the filling. Return to the oven and bake another 20 minutes or until a knife inserted in the center comes out clean. Cool 10 minutes. Slice into squares.
From Delicious Maine Desserts by Cynthia Finnemore Simonds