Mix choc chips, butter vanilla and marshmallows, craisins and walnuts in a large bowl and set aside.
Stir evaporated milk and sugar together in a medium sauce pan. Over medium heat, stir until mixture beings to boil. Turn down heat and continue to boil for 7 minutes. This is what makes the fudge so creamy!
When the seven minutes is up, stir hot liquid into bowl of ingredients and stir until marshmallows and chocolate is melted. Pour into a lightly buttered cookie sheet or 9X13, depending on how think you want your fudge to be.
When the fudge is cooled, score with a paring knife. Cover and let it set for 24 hours. Then dish it up. This is really rich fudge so smaller squares is a good thing.