Heat butter and oil in a skillet over medium-high heat. Add the shallots. Season with salt and pepper, and cook, stirring, until soft, about 2 minutes. Add the poppy seeds and cook, stirring, until fragrant and shallots begin to brown lightly, about 3 minutes. Add the wine and cook until almost all the liquid evaporates, about 5 minutes. Add buttermilk and cream. Cook, stirring, until reduced slightly, about 3 minutes.