Choose 8–10 yams of identical size, guaranteeing that they will cook at the same rate and time. I prefer a smaller yam for this recipe such as Beauregard yams. To guarantee identical sizing, use a vegetable or potato peeler to pare the yams into proper shape and size. Peel yams and place in a large stainless-steel pot with just enough water to cover by approximately ½ inch. Add sugar and vanilla then cook yams until fork-tender, 30–40 minutes, turning the yams with a fork every 7–10 minutes. When tender, there should be no more than ½ inch of water remaining in the bottom of the pot. If there is more, carefully remove the yams and reduce the liquid to ½ inch over high heat. Once liquid is reduced and simple syrup begins to form, reduce heat to simmer. Add butter to the liquid and melt thoroughly. Return yams to syrup then reduce heat to low and cook until yams have absorbed most of simple syrup but are not falling apart. Do not overcook. Serve one yam per guest with an equal serving of simple syrup.