Butter an 8" square baking pan; set aside.
In medium saucepan, combine butter, evaporated milk, sugar and salt; bring to a boil over medium heat; stirring constantly; boil 4-5 minutes, stirring constantly.
Remove from heat; stir in marshmallows, chocolate morsels, vanilla and nuts; stir vigorously for 1 minute or until marshmallows melt and blend.
Pour into butter 8" baking pan.
Cool and cut into squares.
1. Fancy Fudge: substitute 1/4 c. toasted chopped almonds and 1/2 c. finely chopped candied mixed fruits for the pecans or walnuts.
2. Fudge Rolls: spread about 1 c. chopped nuts on waxed paper. Pour warm fudge mixture over nuts. As fudge cools, form into roll; slice.
3. Peppermint Fudge: sprinkle 1/4 c. coarsely broken peppermint candy over top of warm fudge in pan; cool; cut into squares.
4. Upside Down Coconut Fudge: spread 1 c. flaked, toasted coconut on bottom buttered 8" square baking pan. Pour warm fudge over coconut; cool; cut into squares.