Preheat oven to 350 degrees F. Line a large cookie sheet with parchment paper or foil. Lightly grease the foil, if using. Set sheet aside. In a large bowl, beat shortening with an electric mixer on medium to high speed for 30 seconds. Add granulated sugar, brown sugar, baking soda, pumpkin pie spice, and salt. Beat until combined, scraping bowl occasionally. Beat in egg and vanilla until combined. Alternately add flour and milk, beating on low speed after each addition just until mixture is combined.

Spoon batter in 2-inch-diameter rounds about 1/2-inch high onto prepared cookie sheet, leaving 2 inches between each dough round. Bake in the preheated oven for 9 to 11 minutes or until tops are set. Cool on cookie sheet for 2 minutes. Transfer cookies to a wire rack; let cool.

Spread the flat side of half the cookies with a rounded tablespoon of Pumpkin-Ricotta Filling. Top with the remaining cookies, flat sides down. Drizzle or spread with White Chocolate Glaze. Sprinkle glaze with chopped pistachio nuts. Before serving, chill for 30 minutes or until white chocolate is firm. Makes about 20 sandwich cookies.

In a large mixing bowl, whisk together 1 1/2 cups powdered sugar, 3/4 cup canned pumpkin, 1/2 cup mascarpone cheese (half an 8-ounce container), 1/2 cup ricotta cheese, and 1 teaspoon pumpkin pie spice until smooth. Stir in 1/4 cup chopped dry roasted pistachio nuts. Cover and chill for 1 hour.

In a small microwave-safe bowl, place 3 tablespoons whipping cream. Microwave, uncovered, on 50% power (medium) for 30 to 40 seconds or until cream comes to boiling. Add 4 ounces chopped white chocolate (with cocoa butter). Do not stir. Let stand 5 minutes. Stir until chocolate melts. Let stand 5 to 15 minutes before using. The glaze firms up as it stands. If you want a glaze that runs down the side of the cookies, let glaze stand only 5 minutes. If you want glaze that spreads like thin frosting, let glaze stand 15 minutes.

Place filled and glazed whoopie pies in a single layer in an airtight container; cover. Store in the refrigerator up to 1 day or freeze up to 3 months. Thaw in the refrigerator, if frozen. Let stand at room temperature for 30 minutes before serving.