In a large bowl, add the yams, sugar, butter, vanilla and eggs
Using a potato masher, mix all of the ingredients together
Add to a 13x9 baking dish or a casserole dish
Next, add all of the topping ingredients in a separate bowl
Mix together using a fork and creating a "crumb" mixture.
Add to sweet potato mixture right on top evenly
Place in a 350-degree oven for 30-35 minutes or until the top is browned and the marshmallows are melted and golden