Preheat the oven to 350 F with a rack placed in the center of the oven. Line a 12 muffin pan with cupcake liners and set aside. You can also use a mini muffin pan.
Mix the 4 tbsp of whole milk with the vinegar and set aside for at least 5 minutes. This sour milk will make the cupcakes soft and moist.
Whisk the flour, cardamom, baking powder, baking soda, and salt together in a large bowl and set aside.
In a stand mixer or a large bowl, beat the butter until it’s soft (about 1-2 minutes) and then add the sugar and beat until it’s light and fluffy (about 2-3 minutes).
Add the eggs and beat until they are incorporated. Scrape down the sides of the bowl, as needed.
In a separate bowl, whisk the condensed milk and the ½ cup of whole milk together.
In the stand mixer bowl, add the sour milk and the condensed milk and the dry ingredients alternately until all the ingredients are incorporated. Each time, mix on low speed, just until all the ingredients are incorporated. Do not overmix the batter.
Fill the lined tin with the batter until each liner is about 2/3 of the way full.
Bake mini cupcakes for 10-15 minutes and regular cupcakes for 17-20 minutes or until a toothpick comes out clean. Another quick test is to check if the cupcake springs back when gently pressed. If it springs back, the cupcake is done. If a dent remains, then place the cupcakes back in the oven a little longer.
Let the cupcakes cool in the pan for about 10 minutes and then cool the cupcakes on a rack completely before frosting.
Use either a knife or an offset spatula or a piping tip to frost the cupcakes.