Natalie's favorite Sweet potato Pie

1/4 cup of butter
1/2 cup brown sugar
2 cups mashed sweet potatoes
3 eggs
1/3 cup white sugar
1 cup milk  (depending on  richness should determine what milk you use)   I like half and half
1/3 cup dark Karo
1/2 teaspoon salt
1 teaspoon vanilla or 1 inch piece vanilla bean, scraped(use seeds only)
1 teaspoon cinnamon
1/4 teaspoon nutmeg

Mix all ingredients in mixing bowl and Pour into pastry shell.     Preheat oven to 425  cook pie at this temp for 10 min...then lower oven temp to  325 and continue cooking for   35-40 min or until set in middle.