Mix 2/3 cup (one small can) Carnation evaporated milk, 1-2/3 cups sugar, and 1/2 teaspoon salt in saucepan over medium heat. Bring to boil; cook for 5 minutes, stirring constantly. When the milk starts to bubble around edges of pan is when you should start timing the 5 minutes.
Remove from the heat. Add 1-1/2 cups (16 medium) diced marshmallows, 1-1/2 cups semi-sweet chocolate chips, and 1 teaspoon vanilla. Stir vigorously for 1 minute (or until marshmallows melt). Pour into an 8-inch square buttered pan. Garnish with nuts. Cool. Cut in squares (makes about 2 pounds).
For Peppermint Fudge: Sprinkle 1/4 cup of coarsely broken peppermint stick candy over top of fudge in pan.
For Upside-Down Coconut Fudge: Spread 1 cup flaked coconut on bottom of buttered 8″ square pan. Top with fudge.
For Nut Fudge: Add 1/2 cup chopped nuts to fudge mixture before pouring in pan.