Chocolate Cupcakes

I know I have already posted my favorite cupcake recipe, you can find it here.  But there are a lot of ingredients, and sometimes I am in a hurry, or I'm out of most of the things I need.  Like canned pumpkin, which is really hard to find when it is not Thanksgiving!  So, I have tested a lot of other chocolate cupcakes.  A lot of them involve boiling water and cocoa.  And every time I have made any of these cupcakes, they sink.  SINK.  Way down to the bottom of the cupcake liner.  SINKING is not a good thing to see when you are trying to make fluffy cupcakes.  I am not sure what I have been doing wrong, but something is not happening when I make any of these recipes.  I'm sure they are great for other people, but they have not turned out for me.  Any pointers would be great!  Anyway, I had this idea.  All cupcake recipes are basically the same, right?  It's about adding the right amount of sugar, butter, rising agents, and flour..right?  So, if I have a recipe that works for me every time..Vanilla, why not add to it?  Which is exactly what I did, and I must say, I am very pleased with the results. More than pleased.  This is a go to, works every time type of recipe.

Vanilla/Chocolate Cupcakes

1 cup unsalted butter, softened
2 cups sugar
4 eggs
2 3/4 cup all purpose flour
(3/4 cup unsweetened cocoa powder, not the dutch processed, if you want to make chocolate)
1 1/2 tsp baking powder
1/8 tsp salt
1 cup milk
2 tsp vanilla

Preheat oven to 350.  Cream together the butter and sugar for 2-3 minutes, or until the sugar and butter have been well combined, light and fluffy.  Add the eggs, one at a time, letting them mix for 30 seconds before adding the next egg.  (if you need to, like I do, scrape your bowl, making sure that all the butter mixture gets well mixed) In a separate bowl, add the dry ingredients (if you are making chocolate cupcakes, add the cocoa).  In a cup, measure out your milk and add the vanilla.  Alternating dry with wet, add to the butter mix. Fill your cupcake liner with batter.  I use an ice cream scoop..and by the way, if you need a great cupcake liner, I found the perfect and cheapest spot to buy them!  You can find them here.  Bake the cupcakes for 22-24 minutes, or until the cupcake bounces back when lightly pressed.