Using the whisk attachment on the stand mixer, whisk together the mascarpone, powered sugar, and vanilla extract on medium speed until just combined.
Increase to medium-high speed and slowly add the heavy cream. Once completely added, stop the mixer and use a spatula to scrape the sides and bottom of the bowl.
Turn the mixer back on medium and mix until stiff peaks form, about 2-3 minutes. Be careful not to over-mix. Use immediately, or refrigerate the frosting until ready to use.
Notes
Click on the time in the instructions to start a timer!StorageRefrigerate frosting (and any cake that uses the frosting) in an airtight container for 2-3 days. I don't recommend freezing this, because it won't defrost with the same texture. This is really quick to make, so I recommend starting with a fresh batch of frosting. Cooking Tips
Make sure you use the whisk attachment for the stand mixer.
Try not to over-beat the sugar and mascarpone, or the texture may become too soft or become grainy. If this happens, try adding a small amount of heavy cream at a time until the texture improves.