Line an 8 x 8-inch baking pan with foil; grease lightly.

Place the chocolate chips and sweetened condensed milk in large, microwave-safe bowl.

Cook on high for 1 minute.

Remove and stir (if necessary, microwave at additional 10- to 15-second intervals until all the chips are melted).

Stir in vanilla extract.

Fold in marshmallows and nuts.

Press mixture into prepared baking pan.

Refrigerate until ready to serve.

Lift from pan and remove the foil.

Cut into pieces, and enjoy!