Cut an 8" x 12" piece of parchment paper to fit the bottom and up two of the four sides of an 8" square baking pan. (The parchment paper extending the sides of the pan will later be used as handles to lift the fudge out of the pan once set.) Combine the evaporated milk, sugar and vanilla in a tall, medium-sized pot. Bring to a boil over medium-high heat; turn the temperature to medium-low and simmer for 4 minutes. Remove from heat and stir in the chocolate chips, marshmallows and pecans. Stir until the chocolate just melts and bits of the marshmallow are still visible. Pour the mixture into the prepared pan. Cool to room temperature and then cover and store in the fridge until set. Cut into small squares and serve.