In the bowl of a stand mixer fitted with the whisk attachment, or using a hand mixer, combine sugar, cream, vanilla, and salt. Mix at medium-low speed until sugar is dissolved, about 2 minutes. Increase speed to high and continue beating until cream is about as thick as Greek yogurt, about 2 minutes longer. Begin adding cream cheese 2 tablespoons at a time; this should take about 30 seconds all together. Once it is incorporated, shut off the mixer. The frosting will look a bit curdled, like cottage cheese; this is the result of incomplete mixing rather than over-whipping, so don’t be alarmed.