Meanwhile, form pie crust in a 9" pie dish. Poke the bottom and sides of the crust with a fork and set aside in the refrigerator until needed.
Once the yams are cool enough to handle, slice the sweet potatoes in half and then slice off the stringy ends. Add the flesh to a large mixing bowl and beat on medium speed for a few minutes. Stop occasionally to remove any stringy fibers that collect on the beater.
Add eggs, yogurt, vanilla, butter, and half-n-half. Mix on medium until fully incorporated. Add brown sugar, flour, salt, and the remaining spices. Mix on medium until all the ingredients are combined, scraping the sides of the bowl as needed and removing the stringy fibers.
Pour the pie filling mixture into the prepared pie pan. If you have enough dough, use cookie cutters to cut out leaves or another shape to decorate the edges of the pie (optional).
Place the pie on a baking sheet and bake, uncovered, for an hour or until the center of the pie is set. You can test for doneness by inserting a knife into the center of the pie. If the pie is done, the knife should come out relatively clean.
Cool to room temperature before storing in the fridge. The pie will be puffed up when you first remove it from the oven but will deflate as it cools. Serve pie with ice cream, whipped cream, or cool whip if desired.