Three that are really good and I’ve found to be long-lasting (although I never froze them so who knows?):
Lemon buttercream frosting
3/4 cup unsalted butter, softened
3 1/2 cups powdered sugar
2 tablespoons heavy cream
2 teaspoons fresh lemon juice (sometimes I add a bit more; see note below re lemon zest)
1/4 teaspoon vanilla extract (sometimes I leave this out)
1 teaspoon finely grated lemon zest (note: I’m a lemon freak so I actually put in basically the rind of a whole lemon; this renders the buttercream frosting really, really lemony, which nicely offsets the richness)
Beat the butter on medium speed until creamy, about 30 seconds, then gradually add the powdered sugar on low, then add the rest of the ingredients. Increase the speed to medium-high, and beat for about 3 minutes, or until the frosting is light and fluffy.
Mint buttercream frosting
1 cup butter
4-5 cups powdered sugar, sifted
1/4 cup milk
1/8 teaspoon all natural peppermint extract (be careful! start with drops and taste until you get the right taste, as you don’t want the mint to be overwhelming)
Same instructions as above.
Peanut butter frosting
This one is great for making a peanut butter and jelly cupcake (any flavor cupcake is fine, but you can stuff some jelly in the cupcake and then frost with this)
1/2 cup butter, softened
1 cup creamy peanut butter
3 tablespoons milk, or as needed
2 cups confectioners’ sugar
Same instructions as above, except add the milk one tablespoon at a time until you get the right consistency.
All of these are pretty shockingly easy to make and the taste is so much better than premade frostings that I’m a convert. I’ll still use cupcake mixes, but I believe that a good quality stuffing for the cupcake and a good quality frosting mean that the cake is pretty much a minor player.