On a floured surface, roll the pie dough to about 12-13 inches in diameter. Carefully roll up the dough around the rolling pin, then unroll into a 9-inch pie pan. Trim the edge all the way around so it extends just slightly past the dish, then fold the edges under and crimp. Cover with plastic wrap or a clean dish towel and refrigerate for 45 minutes to 2 hours.

Peel and cut the sweet potatoes into 2-inch pieces. Place in a large pot and cover with cold water, then bring to a boil. Reduce the heat to medium and simmer until the potatoes are fully tender with no resistance when pierced with a fork, 15-30 minutes. Drain into a colander. Alternatively, you can use the microwave (see notes).

Return the sweet potatoes to the pot and mash with a potato masher until smooth. Measure out 2 cups and discard any remaining sweet potato (or save for a different use).

Return the 2 cups to the pot and add the brown sugar, cinnamon, nutmeg, coriander, salt, butter, and half the evaporated milk. Simmer on medium-low heat, stirring frequently, for about 5 minutes. You want to get the mixture as smooth as possible. If you have one, use an immersion blender toward the end to help puree the ingredients (if not, continue using the potato masher). Remove the pot from the heat.

In a medium-sized bowl, thoroughly whisk together the remaining evaporated milk, cream, granulated sugar, eggs, and vanilla extract. Pour into the sweet potato mixture.