Make the cupcakes: Preheat the oven to 350°F. Prepare two cupcake pans with 14 liners (you may need more or less depending on amount of batter).
In a small bowl, whisk the milk and vinegar. Set aside for 10-15 minutes, until curdled.
In a large mixing bowl or the bowl of a stand mixer fitted with a paddle attachment, whisk the flour, sugar, baking powder, baking soda, salt, and spices. Add the milk mixture, melted butter, and vanilla and beat with a hand or the stand mixer until just combined.
Pour about 3 tbsp (45 ml) of batter into each cupcake liner. Bake in the preheated oven for 16-20 minutes, until a toothpick inserted into the center of a large cupcake comes out clean or with just crumbs. Allow the cupcakes to cool completely.
Meanwhile, make the frosting: Place the butter into a large mixing bowl or the bowl of a stand mixer fitted with a paddle attachment. Beat for a few minutes, until light and fluffy. Add the powdered sugar, spices, vanilla extract, and 1/2 tablespoon of milk and beat again, until light and fluffy. If necessary, mix in more milk, approximately 1 teaspoon at a time, until the desired consistency is reached. Scrape the sides as necessary. To remove air bubbles, use a rubber scraper to stir the buttercream a bit and press it up against the sides of the bowl.
Frost and decorate the cupcakes: Place the frosting into a piping bag fitted with a Wilton 2D tip. Frost a swirl on top of each cupcake. Enjoy!