Step 1

Grease a 9x13-inch pan.

Step 2

In a large, heavy saucepan over medium heat, add the sugar, the margarine, and the evaporated milk, and stir to dissolve the sugar.

Step 3

Bring the evaporated milk mixture to a boil and cook, while stirring, for 5 minutes.

Step 4

Transfer the evaporated milk mixture from the heat.

Step 5

Add the chocolate chips to the evaporated milk mixture and stir until they melt and the mixture is thoroughly combined.

Step 6

Stir the marshmallow cream into the evaporated milk-chocolate mixture until it is incorporated.

Step 7

Mix the walnuts and the vanilla into the fudge mixture.

Step 8

Pour the fudge into the prepared pan and use an offset spatula to spread and flatten it out.

Step 9

Let the fudge cool for at least 1 hour.

Step 10

Cut the fudge into squares and serve.