Preheat and prep: Preheat your oven to 350℉ (180℃). Line a 12-cup muffin pan with nonstick cupcake liners.
Mix dry ingredients: In a large bowl, whisk together flour, sugar, cocoa powder, baking powder, baking soda, and salt.
Mix wet ingredients: In a separate bowl or large measuring cup, whisk together plant-based milk, oil, vinegar, and vanilla.
Combine: Pour the wet ingredients into the dry and stir until just combined. Don’t overmix, some lumps are fine. Overmixing can lead to dense or flat cupcakes. A light hand = fluffy cupcakes!
Bake: Evenly divide the batter among the cupcake liners. Bake for 20–24 minutes, or until a toothpick inserted into the center comes out clean.
Make the frosting: In a large bowl or the bowl of a stand mixer, beat together vegan butter, powdered sugar, cocoa powder, and vanilla on low speed until combined. Increase to high speed and whip until light and fluffy, about 1 minute. If the frosting is too thick, add plant-based milk 1 teaspoon at a time until smooth and spreadable.
Frost and decorate: Once cupcakes are fully cooled, frost using a spatula or piping bag. Top with sprinkles, nuts, shaved chocolate, or anything fun! (If the frosting softens, chill for 10–20 minutes to firm it up before piping.)