In a small bowl, combine the milk and apple cider vinegar. Let sit for 5 minutes. Heat a nonstick skillet (see note) over medium-high heat for a few minutes, then reduce the heat to medium. While the pan is heating, in a large bowl, mix the flour, baking powder, vanilla bean powder (if using), and salt. Add the milk and vinegar mixture to the dry mixture and whisk to combine. Fold in any optional add-ins you like. Using a ladle, scoop 1/4–1/3 cup of the batter into the hot pan, fitting as many as you can without allowing the pancakes to touch. Cook for several minutes, until small bubbles form on the outer edge and in the center and the pancakes starts to look dry on the top. Flip the pancakes and lightly cook the other side for about a minute, then transfer to a plate. Repeat until all the batter is used.