Microwave the butter in a large, heatproof bowl on high for 1 minute until it's melted. Then, add in sugar and evaporated milk and mix well. Microwave on high for another 3 minutes. Remove and stir, scraping down the sides of the bowl. Place the bowl back in the microwave and heat it on high for another 5 minutes, or until the mixture comes to a boil. Remove and stir, then microwave the mixture again for 2 more minutes. Carefully remove the hot bowl. Mix in chocolate chips until they're melted. Stir in marshmallow creme, vanilla extract and 1 cup of chopped pecans.
Pour the marshmallow fudge mixture into a lightly greased 9 inch x 9 inch glass dish. Top with the remaining 1 cup of chopped pecans. Allow it to set at room temperature for at least 2 hours
Cut the marshmallow fudge into squares — this recipe makes 16 large squares. Enjoy a square or two for yourself with family. If you're making this recipe as a present, then place the fudge in small baking gift boxes, or wrap them in cellophane. You can cover and chill any leftovers for up to 1 week.
Feel free to mix in chopped peppermint candies, marshmallows or other complementary toppings.