Boil sweet potatoes in a covered pot until they become tender. It helps to place a brown paper bag over the sweet potatoes during the boiling process. This keeps the moisture in the pot and shortens the time it takes to properly boil the potatoes.
Drain the water from the pot and run cold water over the potatoes. Drain off the water and let potatoes sit for 30 minutes.
Peel potatoes and mash in a large bowl. Beat the eggs until the whites disappear. Melt 1/2 stick butter and pour it over the mashed potatoes along with the milk, sugar, flour, cinnamon, nutmeg, lemon and vanilla extracts. Get as many of the lumps out of the mixture as possible.
Preheat oven to 350 degrees. Spray pie pan wit Pam, press the pie crust into the pan, bake for 1 hour.