1. Preheat oven to 350ºF. Line 12-cup muffin pan with paper liners.
2. Combine milk and vinegar in a small glass dish and set aside to sour.
3. In a large mixing bowl, combine flour(s), sugar, baking powder, baking soda, and salt. Stir until thoroughly mixed.
4. Mix in oil, vanilla, and sour milk, beating just until smooth.
5. Fill muffin cups, about 1/4 cupful or 3/4 full. Place into the preheated oven and bake 16–20 minutes, just until cupcakes have domed and a toothpick inserted in the center comes out with a few moist crumbs.
6. Place the pan on a cooling rack for a few minutes then remove the cupcakes to cool completely before frosting. Makes 14–16 cupcakes.

Vanilla Buttercream:

1. In a medium bowl, beat softened butter until creamy. Add powdered sugar 1/2 cup at a time, blending until well combined. Add enough powdered sugar until you reach your desired consistency/sweetness. Beat in vanilla extract, and 1-3 teaspoons milk/water, if buttercream gets too stiff. Once everything is added, beat buttercream 2-3 minutes to make extra fluffy.
2. Cover well and store at a cool room temperature for 2–3 days or in the fridge for up to 1 week.
3. I used Wilton tip 1M to pipe the buttercream on these cupcakes. Depending on how high you like your frosting, you may need an extra batch of buttercream.