I've been making this Buttercream Icing forever! I don't even need measure it out - and neither do you!
What you are looking for is the consistency - thicker icing for decorating - thinner icing for a pour over, and thinnest for a drizzle. If its too thin, add more sugar to thicken. Too thick? Add a teaspoon of water to thin.
This recipe should be enough to pipe a swirl on 24 cupcakes with leftovers - but it will depend on how thick your icing is and much you use on each cupcake.
Here's the basic recipe:
1 cup Butter (that's half a brick) $1.48
4 cups Icing Sugar (that's the small 500g bag) $0.64
Total Cost: $2.27 = $0.09 per Cupcake
1. Beat the Butter with your mixer. Add Vanilla and beat until combined.
2. Slowly begin adding the Icing Sugar to the Butter, until the whole bag is incorporated. It will be very thick.
3. Slowly add a drizzle of water, beating well between additions until you've reached the desired consistency. For the sake of this recipe, I used a measuring cup, and this batch took almost 1/4 cup of cold water.
Tint to the desired colour - I used Food Colouring Pastes - but if you were using a liquid colour, I would add it to the mixture BEFORE adding the water.
If you want a white icing, substitute the Butter for Shortening - same amount - and I still used regular Vanilla in the picture above. Shortening is also cheaper!
If you want a true white, either use a clear Vanilla, a different clear extract flavour (Almond is great too!) or omit altogether.
Another tip - if the room temperature is warm, butter melts very easily! Shortening has a higher melting point, so I would recommend using the shortening to preserve the look of the icing in warmer areas. I'm thinking of backyard parties in July! :)