This is my go to recipe that I have been using for years and it has never failed me. I add a little bit of Crisco to the butter (yes I said Crisco) and also cream to make it smooth and light, yet holding up when you pipe it. The more you beat it, the better it is. This dissolves the powdered sugar. Speaking of powdered sugar, I never use anything but C&H powdered sugar. I could be a poster child for them. I have tried many other brands and they are all to grainy for me. I use this for piping cupcakes or frosting and under fondant for cakes. Give this a try in your next baking adventure.
1 cup butter (2 sticks)
1/2 cup shortening (white, not butter flavored)
4 cups powdered sugar
1 teaspoon vanilla (use good vanilla, not the cheap imitation kind. I use Blue Cattle Truck.)
1-2 tablespoons or more whole milk or cream to desired consistency. One tablespoon at a time. I usually use cream.
In a bowl of mixer cream butter and then add shortening to cream together until light and fluffy. Add half of the powdered sugar and blend. Add vanilla and the rest of the powdered sugar and mix well. Add the milk OR cream and beat until light and creamy.
Tip - For chocolate frosting you can whisk 1/2 cup of unsweetened cocoa to the powdered sugar. This will make a milk chocolate frosting in looks and taste.