1.Preheat oven to 350 degrees, line cupcake pan with foil or paper cups and mist the cups and around the cups a little.
2.In a large mixing bowl, mix the cake mix, seltzer, baking powder, and flour with a rubber spatula. Make sure you get all the way underneath to mix in all the dry ingredients.
3.Add the vanilla extract.
4.Using a hand held mixer, beat for about 1-2 minutes until batter is smooth and fluffy.
5.Add the chocolate syrup by swirling around the batter. Now with a wooden skewer or butter knife, twist and swirl the chocolate around (without mixing it in to look like a chocolate batter). You want this to look marbleized.
6.With an ice-cream scooper, fill the cups half way. Now sprinkle in most of the chocolate chips, leave some out for the topping of each cupcake.
7.Fill the rest of cups with the batter. You may have enough batter for 13 cupcakes or even 14 cupcakes, so don’t over fill the cups or it will be hard to take out of the pan when they are baked. Just save the batter and make two more cupcakes if you want when the first batch is done baking.
8.Sprinkle the remaining chips over each cupcake.
9.Bake for about 15-20 minutes. Turn pan around after 8 minutes for even baking. Test with a wooden skewer or toothpick and it should come out clean or with dry crumbs.
10.Let cool in the pan on a cooling rack for at least 30 minutes and then pop out!
Enjoy the deliciousness!