With the stand mixer, beat together the pumpkin, eggs, brown sugar, oil, and molasses. Scrape down the bottom and sides of the bowl, then beat in the salt, spices, baking powder, and baking soda.
Add the flour to the wet ingredients and beat on low for about 1 minute, until all of the flour is wet. Scrape the bottom and sides of the bowl, then beat on medium for a short time until the batter looks smooth. Scoop and drop the batter onto the prepared baking sheets, spacing 2 inches apart to allow for spreading.
Bake the cookies for 10 to 12 minutes, until they feel firm to the touch. To test, gently press your finger in the center, and a slight indentation should remain. Remove the cookies from the oven and allow them to sit on the pans for another 5 minutes, then transfer to a wire rack. Cool completely before adding the filling.
Filling
Put the butter, cream cheese, and vanilla in the mixer bowl and beat on medium-low speed for about 1 minute, until the mixture is smooth and thoroughly combined. Decrease the speed to low and add the confectioners sugar a little at a time. Beat on medium until the frosting is smooth, about 1 minute.
Assemble
Spread the flat side of half the cookies with the filling. Top with the remaining cookies. Because these cookies tend to be sticky, wrap each pie individually in plastic wrap for storing. Keep the cookies in the refrigerator.
Notes
Variations
ORIGINAL FILLING RECIPE 1 tablespoon unflavored gelatin 2 tablespoons (1 ounce) cool water ½ cup (1 stick, 4 ounces) unsalted butter ½ cup (4 ounces) cream cheese (reduced fat [Neufchâtel] or full fat) 2-¼ cups (9 ounces) confectioners’ sugar 2 tablespoons finely chopped crystallized ginger1. In a small heatproof bowl, combine the gelatin and water and set aside for the gelatin to soften. In a large mixing bowl, beat together the butter and cream cheese until fluffy. Heat the gelatin and water very gently (in a larger bowl of hot water, or at low power in the microwave), stirring to dissolve the gelatin. Set it aside.2. Add half the confectioners’ sugar to the butter/cream cheese mixture, beating well. Add the gelatin and mix to combine. Add the remaining confectioners’ sugar, mixing until blended, then stir in the ginger.