Tips For Making Cream Cheese Frosting 

• Use softened butter and cream cheese. This is important. If either one is too cold they won't incorporate and turn into a smooth frosting. You will end up with a lumpy cream cheese frosting. I used to recommend using cold cream cheese frosting so it could be piped. But no longer. I found that when I did that it was not smooth. Pipeable maybe. But not smooth. So soften both. Being able to pipe will come down to ratios of butter to cream cheese which this recipe has.  And if you need to soften your butter quickly I have 3 easy ways to do that for you. But basically you can leave them out on the counter for an hour or so until softened. 
• Cream The Butter First. Then add in your cream cheese. Otherwise you may end up with a weird mouthfeel if you do this the other way around. A tip I picked up from The Kitchn.
• Scrape down the bowl as you go. Sometimes the butter and cream cheese will stick to the bottom of the bowl or beater and not be mixed in evenly. So stop and scrape the bowl down with a sturdy silicone spatula to ensure that everything is being mixed in. 
• Use Full Fat Brick Style Cream Cheese. Sorry but now is not the time to save those calories. 
• Use unsalted butter. Different brands of butter can use varying amounts of salt in their salted butter. So you want to control the amount of salt by adding it yourself. 
• Sift If Piping Your Cream Cheese Frosting. I usually don't have a problem with powdered sugar lumps. But if you want to be on the safe side, especially if you are going to use a piping bag with this frosting, you can sift your powdered sugar first. This will ensure no lumps get stuck in your piping bag. If you're not a fan of sifting (and neither am I!) you can also just whisk your powdered sugar in a bowl before adding it to the frosting.
• Frost: This will easily frost a dozen cupcakes, a 2 8-inch layer cake or 9x13 cake. If you are frosting a larger cake (like a 9-inch layer cake) and if you plan on adding embellishments like rosettes then I recommend making a double batch. 
• Make Ahead: I make this up to 5-7 days in advance and store in the refrigerator. Or I will freeze the frosting for up to 3 months. Just simply thaw in your refrigerator overnight. 
• To thicken:  Add in 2 tablespoons of powdered sugar. Mix again. You can add more if you’d like but I recommend adding in a couple tablespoons at a time. Or add in a one tablespoon of cornstarch. (if you it thicker, but not sweeter) Start with one tablespoon and mix. Continue to add in one tablespoon at a time until your desired thickness.