In large mixing bowl, add butter and heat in microwave until fully melted.
Add sugar, evaporated milk and whisk until combined.
Heat in microwave for 2-3 minutes, whisking every 30 seconds until sugar is dissolved and your candy thermometer reaches 234 degrees F.
Remove bowl from microwave and add chocolate chips.
Whisk until chocolate is fully melted and mixture is smooth.
Add marshmallow creme, vanilla extract and mix well until you no longer see any white streaks.
Stir in walnuts.
Pour mixture in an 8 or 9 inch square pan, lined with wax paper. Use 8 inch pan for thicked fudge pieces. Use 9 inch pan for thinner/ flatter fudge pieces.
Cool completely at room temperature.
Then, chill in fridge for 2-3 hours until firm.
Use a sharp knife to cut small square pieces. Enjoy!