Chill a large bowl and whisk in the fridge or freezer. Have your blender at the ready.
Pour ¼ cup of the cream into a large heatproof measuring cup and add the sugar (place the remaining cream back in the fridge.)
Melt the butter in a small skillet over medium heat. Cook, stirring frequently with a rubber spatula, until the butter turns deep golden and smells nutty, 2 to 4 minutes.
Pour the butter and brown bits into the measuring cup of cream and sugar and stir to combine; the mixture may look oily on top. Cool to room temperature, stirring occasionally, until thickened like honey.
Add the remaining 1 ¾ cups (420g) of chilled heavy cream with the vanilla and salt in a blender. Add the cooled butter mixture and immediately blend on low for 5-10 seconds until thickened but still fluid.
Transfer to a large bowl and use a whisk to whip the cream to the texture of thick yogurt. If the cream looks broken or overwhipped at any point, use a spatula to fold in a splash of additional cream.
Store covered in the refrigerator for up to three days. Makes about 4 cups and will frost a half sheet cake or 18-24 cupcakes.
