Melt the butter in a saucepan or small pot over medium heat. Peel and dice your shallot and add it to the melted butter and sauté for 3-5 minutes until fragrant and soft.
Add the sherry, salt, and pepper and bring to a simmer, still over medium heat. Continue to simmer stirring occasionally until it reduces and most of the liquid has evaporated.
Add the cream and continue to simmer, stirring frequently, assessing the consistency. When you are happy with the thickness, remove from heat and serve hot. The longer you simmer, the thicker your sauce will be. For serving over pasta, keep it on the thinner side to easily toss. Otherwise, I like it thick!
