Add the butter to a large bowl or stand mixer fitted with a whisk attachment and whip at high speed for 5 to 7 minutes, scraping down the sides of the bowl every minute or so.
1 cup unsalted butter
With the mixer on low speed, slowly pour the sweetened condensed milk into the butter.
14 ounces sweetened condensed milk
Scrape the sides and bottom of the bowl then whip at high speed for 1 until full incorporated.
Notes
This frosting is best made fresh and consumed shortly after. Keep in a cool area until ready to serve - even a 70 degree room can cause the frosting to start melting. You can place frosting cakes, cupcakes, and cookies in the fridge to stay firm, then pull out 30 to 60 minutes before enjoying - although you may not get quite the consistency you would have had with the fresh frosting.
Vanilla or almond extract may be added to the frosting.
1/4 teaspoon of salt may be added if desired.
1/4 cup of cocoa powder may be added for a chocolate flavor.
Storage Instructions: Store this buttercream in an airtight container in the refrigerator for up to a week. Once it’s been refrigerated the buttercream will need to be re-whipped before using it. To do so, first, allow it to come to room temperature. Then re-whip with a stand hand mixer.
How Many Cupcakes Will This Recipe Be Able To Frost? This recipe for Russian Buttercream yields 3 cups of frosting. Giving you plenty to frost about 2 dozen cupcakes or a cake!
What Should I Do If My Russian Buttercream Has Separated? If the frosting has separated once you’ve added the condensed milk, then the butter was likely too warm or soft from the start. To fix this, just place the bowl of Russian buttercream into the fridge for 10 to 15 minutes. After, re-whip the frosting and it should come together just fine!
How Come My Buttercream Didn’t Turn Out Light And Fluffy? The butter was likely too cold when you began making the frosting. No worries though this is a simple fix! Place half of the frosting into a microwave-safe bowl and heat it in the microwave for about 10 seconds. Next, place the heated half of the buttercream back in with the remaining half. Then continue to beat the mixture until it becomes light and fluffy.