In a medium saucepan, heat brown sugar and butter over medium heat, whisking constantly, until butter is melted, sugar dissolves, and bubbles form around edges of pan, 3 to 5 minutes. (Do not boil.) Add cream, ginger, vanilla bean paste, and salt, whisking until well combined, and cook until bubbles form around edges of pan, about 5 minutes. (Do not boil.) Serve warm.