Line a 9x13-inch pan with heavy-duty aluminum foil, extending foil over edges of pan. Lightly coat foil with 1/2 of tablespoon butter; set aside.

In a heavy 4-quart saucepan, melt 1 tablespoon of butter over medium-low heat. Add evaporated milk and marshmallow creme, stirring until marshmallow creme starts to dissolve.

Add sugar and stir until well dissolved.

Bring mixture to a slow boil over medium-low heat, stirring almost constantly (a rubber scraper allows you to scrape the bottom and sides of the pan to avoid scorching). This will take 15-20 minutes, depending on the temperature of the burner. A "low boil" is when lots of small bubbles form (especially around the edges of the pan).

Continue cooking and stirring over low heat for 5 minutes.

Remove pan from heat and turn off burner. Stir in chocolate chips. Fold chips into hot sugar mixture until smooth.

Pour into prepared pan. Tap pan on countertop a few times to evenly distribute the fudge and to draw any air bubbles to the surface.

Allow to cool; cover and refrigerate.

When completely chilled, remove fudge from pan using the edges of the foil. Pull back the sides and cut into one inch cubes.

Store in air-tight ziploc bag or wrap in plastic wrap and keep in an air-tight container.

Store in refrigerator.