We bought one small can (29 oz.) and one large can (40 oz.) of yams (they really are sweet potatoes!). We reserve the remaining 1-2 cups of sweet potatoes for another use. The drained sweet potatoes we put into the bowl of our KitchenAid mixer since we were being lazy. This of course could have been done in a large bowl.
We melt 8 tablespoons of butter in a glass measuring cup in the microwave (2 minutes at 20% power). We add this to the bowl of sweet potatoes, along with the sugar and milk. We beat this on low power and then we add the eggs, one at a time, and beat on medium speed until incorporated. We add the vanilla, stir well with the mixer, and then remove the bowl.
We spread half of the mixture into a 9 inch x 13 inch glass baking pan. To the rest of the mixture, we add the .5 cup of coconut and stir well with a rubber spatula.
In the glass measuring cup, we melt the remaining butter in the microwave for 1 minute at 20% power. In our food processor, we combine the flour and pecans. We pulse until the pecans are crushed. Next we add the brown sugar and pulse to combine. With the machine on, we pour in the butter through the feed tube. We then add the rest of the coconut and pulse to combine. This is the topping for the sweet potatoes that are mixed with the coconut. This made a lot of topping, so maybe next time we can cut this in half, but…..it is thanksgiving!
We spread the coconut-sweet potatoes into the other half of the baking dish and top these with the pecan-coconut topping. We bake this in the oven for an hour. We want it bubbling, the crust hardened, and the sweet potatoes that are not covered lightly browned. We are not eating right away, so we cool it for about a half hour and then cover with plastic wrap and refrigerate.
About 40 minutes before it is to be served, we reheat it at 350 degrees. Originally, we thought we could microwave it, but decided against it because of the sugary crust. Next time, we could try refrigerating it unbaked and then bake when ready. When it is hot, we add the marshmallows to the sweet potatoes without the coconut, spreading them in one layer. We bake for about 5 minutes and then broil them, watching carefully, until the marshmallows are golden.