1 (4 ounce) stick plus 3 tablespoons unsalted butter, softened
3 1/2 cups light brown sugar
4 eggs
2 cups pur?d cooked or canned pumpkin
3 1/3 cups flour
1 1/2 teaspoons baking powder
1 teaspoon baking soda
1 teaspoon cinnamon
1/2 teaspoon ground ginger
1/4 teaspoon ground mace
1 cup chopped walnuts

Preheat oven to 325 degrees F.

Before starting batter, wash 8 (1-pint) wide-mouth canning jars with lids in hot, soapy water and let them drain, dry, and cool to room temperature. Generously grease insides of jars.

With an electric mixer, beat together butter and about half of brown sugar until light and fluffy. Beat in eggs, then remaining sugar. Beat in pumpkin. Set aside.

Sift together flour, baking powder, baking soda, cinnamon, ginger and mace. Gradually add to pumpkin mixture in thirds, beating well after each addition to make a thick batter. Stir in walnuts. Spoon 1 level cupful of batter into each jar. Carefully wipe rims clean, then place jars in the center of preheated oven. Bake 40 minutes.

About 10 minutes before cakes are done, bring a medium saucepan of water to a boil. Put in jar lids, cover, and remove from heat. Keep lids in hot water until they're used. When cakes are done, remove jars from oven one at a time. If jar rims need cleaning, use a moistened paper towel. Carefully put lids and rings in place, then screw tops tightly shut. Place jars on a wire rack; they will seal as they cool.