In a small saucepan, melt butter over medium heat. Add brown sugar, golden syrup, vanilla, and salt, whisking until dissolved. Add cream, and bring to a boil; boil for 3 minutes. Transfer to a small bowl. Let cool to room temperature before using.
Notes
If the Golden Caramel is too thick to pour, heat it in the microwave in 10-second intervals until pourable. You don’t want it hot, though, because it will melt your buttercream. All you are looking for is a slow pour.
Recipe by Bake from Scratch at https://bakefromscratch.com/golden-peanut-butter-cake/