Season the livers with salt and pepper. Heat the butter in the sauté pan over medium heat until it foams and subsides. Add the livers to the pan and sear on both sides, about 3 minutes per side. Remove the livers and allow to cool for a few minutes.
Place the livers in the blender. Return the pan to the heat and stir in the vinegar, scraping all that goodness from the bottom of the pan