I cook the yams in the microwave, then refrigerate. On day of dinner, take them out, peel them and cut them up in your baking dish, then add the sauce ingredients and bake in the oven according to your recipe. Even if you don't cook the yams a day ahead, it always speeds things up if you microwave the sweet potatos until soft first. But don't cook them too long, you want them a little under-cooked so they peel and cut easily and don't fall apart. Plus cooking them with the sauce will cook them more too.