Grease a 9x13-inch pan.
Mix sugar, margarine, and evaporated milk in a large, heavy saucepan over medium heat, stirring to dissolve sugar. Bring mixture to a full boil for 5 minutes, stirring constantly.
Remove from heat and stir in chocolate chips until melted and thoroughly combined. Beat in marshmallow creme, walnuts, and vanilla extract. Transfer fudge to the prepared pan and let cool before cutting into squares.
To make in microwave, melt margarine in a 4-quart microwave-safe dish and mix sugar and milk into the margarine. Microwave mixture until it begins to boil, about 5 minutes on high, and stir after 3 minutes. Scrape bowl and continue to boil on high for 5 1/2 more minutes. Remove from microwave and stir in chocolate chips until melted, then stir in marshmallow creme, walnuts, and vanilla extract. Pour into prepared baking pan.