Preheat your oven to 350°F (175°C) and prepare cupcake liners in a standard muffin tin.

In a stand mixer, beat together the butter, zest of oranges, all spice, cardamom, nutmeg, and vanilla bean until light and fluffy.

Gradually add sugar, then incorporate eggs one at a time, beating well after each addition.

Whisk together flour, baking powder, and salt; gradually mix into the butter mixture along with the buttermilk.

Fill cupcake liners halfway with batter and bake for 18-20 minutes, until a toothpick comes out clean.

Combine sugar and water in a saucepan and cook until reaching 245°F (118°C). In a separate bowl, whip egg whites until stiff peaks form.

Gradually add the syrup to the egg whites while whipping until glossy and cool; then mix in cocoa powder and butter.

Whisk together orange juice, egg yolks, and sugar in a saucepan over medium heat until thickened, then stir in butter until melted.

Frost cooled cupcakes with the buttercream, drizzle with orange curd, and decorate with zest and sprinkles.