Need Help With A Recipe

I have been searching for the right cupcake recipe to use to start my cupcake business. Recipes on the internet can be incomplete or just plain nonsense recipes that don’t work. I found one that I used just once but I do not think it is accurate. I had to keep adding Milk because it was so thick. I think maybe it had too much flour. I was happy with the texture and taste but there can be improvement. Here is the recipe. Please share your opinions on what should be different. I want to get this recipe just right.

Basic Cupcake Recipe

1 cup milk
4 cups flour
5 tsp baking powder
2 sticks of butter
2 cups of sugar
4 eggs beaten
1 tsp vanilla extract

cream together butter and sugar until light and fluffy. add beaten eggs, milk and vanilla. sift flour and baking powder together then add to the mixture. bake at 350 for 10 to 12 min (they weren’t done yet but i think its all the milk i had to add)

There is is. Please help.

How many sticks of butter make the 2/3 cup?