Add the butterscotch beer or cream soda to a large pot. Simmer over medium heat until it reduces to ½ cup. This usually takes around 20-30 minutes. Remove from the heat and let it cool until it's just slightly warm to the touch before using in the cupcakes.
Preheat oven to 350 degrees. Line 2 standard cupcake pans, or one large 24 cup capacity pan, with liners. Set aside.
In a medium bowl whisk together the flour, baking powder, baking soda and salt. Set aside.
In a large bowl cream the butter, brown sugar and granulated white sugar together with an electric mixer, or a stand mixer, for 1-2 minutes or until fluffy.
Add in the eggs, vanilla and butter extract and mix until pale in color, about 1-2 minutes.
Add in the butterbeer reduction and melted and slightly cooled butterscotch chips. Mix until combined.
Add in the dry ingredients and buttermilk a little at a time until everything is combined. Mix until the batter is smooth.
Divide the batter evenly between the 24 liners, each should be about ⅔ way full.
Bake the cupcakes for 14-18 minutes or until a toothpick comes out clean from the centers. (They will bake quickly.)
Let the cupcakes cool in the pan(s) for 5 minutes, then transfer them to a cooling rack to completely cool.