Preheat the oven to 350°F (175°C). Line a 12-cup muffin tin with paper liners and lightly spray or grease the liners.

Sift together the all-purpose flour, baking powder, baking soda, fine sea salt, ground cinnamon, ground ginger, ground nutmeg, and ground cloves into a large bowl. Stir to combine and set aside.

In a mixer, beat the softened unsalted butter with the light brown sugar and granulated sugar on medium speed until pale and fluffy, about 3 to 4 minutes.

Add the eggs one at a time, beating well after each addition, then mix in the vanilla extract.

With the mixer on low, add the pumpkin purée, vegetable oil, and buttermilk and mix until combined; the batter will be thick but smooth.

Add the dry ingredients to the wet mixture in two additions, mixing on low until just combined after each addition. Fold in cocoa powder now if using.

Divide the batter evenly among the 12 liners, filling each about two-thirds full, and bake for 18–22 minutes until a toothpick comes out with a few moist crumbs.

Let cupcakes cool in the pan for 5 minutes, then transfer to a wire rack to cool completely before frosting.

Pulse graham crackers to fine crumbs, then mix with melted unsalted butter and 2 tablespoons granulated sugar until moistened. Press about 2 tablespoons of the crumb mixture into the bottom and up the sides of 4–6 cupcake liners to form crusts and bake for 6–8 minutes to set.

Whisk together 1 egg, dark brown sugar, cornstarch, salt, and heavy cream until smooth, then stir in 1/2 cup pumpkin purée. Divide the filling among the crusted liners and bake at 350°F (175°C) for 18–22 minutes until centers are mostly set.

For spiced buttercream, beat 3/4 cup softened unsalted butter until smooth. Gradually add 3 to 3 1/2 cups confectioners' sugar, alternating with vanilla. Add 1/2 teaspoon ground cinnamon and a pinch of nutmeg, beating until light and fluffy; add milk 1 teaspoon at a time to reach piping consistency.

Optionally beat the softened cream cheese until smooth and fold into a portion of buttercream to make a cream-cheese buttercream for half the cupcakes.

Divide the buttercream into two bowls; tint one soft orange and leave one creamy beige. Fit piping bags with an open star tip and a round tip for different decorations.

Pipe large star swirls of beige buttercream on 6 cupcakes and dust each with ground cinnamon. Reserve these as the classic spiced swirl cupcakes.

Shape small balls of orange fondant into pumpkins, indenting with a toothpick to create ridges. Attach a tiny green fondant stem or leaf and dust lightly with cornstarch or a smear of vegetable shortening if needed. Place pumpkins on top of buttercream mounds on 4 cupcakes.

For the mini pie cupcakes, allow the baked filling to cool and set fully. If desired, pipe a small white buttercream star in the center of each and dust lightly with cinnamon.

Arrange the cupcakes in an alternating pattern in a box or on a platter. Lightly sprinkle sanding sugar or edible sprinkles if using, then store refrigerated until serving.

To serve, bring refrigerated cupcakes to room temperature for 20–30 minutes to restore buttercream texture and ease of biting.