Preheat the oven to 375°F (190°C). Grease 22 muffin cups or line them with paper liners to prevent sticking.
Sift together the flour, 1 teaspoon of cinnamon, nutmeg, ginger, clove, allspice, salt, baking powder, and baking soda in a large bowl. Set aside.
In a stand mixer fitted with the paddle attachment, beat ½ cup (115 g) of butter with white sugar and brown sugar until light and fluffy. Add the eggs one at a time, mixing well after each addition.
Stir in the milk and pumpkin puree until fully combined.
Gradually add the dry ingredients, mixing just until incorporated. Divide the batter evenly among the prepared muffin cups.
Bake for 20–25 minutes, or until the tops are golden and a toothpick inserted in the center comes out clean.
Place the egg whites and ⅓ of the sugar in a stand mixer bowl and whisk on medium-high speed until soft peaks form.
In a small saucepan, combine the remaining sugar with ⅓ cup (80 ml) of water and heat over medium without stirring until it reaches 240°F (115°C) on a candy thermometer.
With the mixer running, carefully drizzle the hot syrup between the side of the bowl and the whisk. Continue whipping until the mixture cools completely, about 10–15 minutes.
When the meringue is thick and glossy, beat in the salt. Add the butter a few pieces at a time, mixing until smooth and silky. Beat in the vanilla extract. If the buttercream is too soft, whip on high speed until firm.
Let the cupcakes cool completely before frosting with Italian Buttercream.
Enjoy your perfectly fluffy pumpkin cupcakes topped with silky buttercream.