Separate pineapple from juice, saving juice. Mix together pineapple juice, honey, lemon juice, soy sauce, vinegar, cornstarch, and gingerroot. Toss together mushrooms and green onions.
Cut out 8 (15-inch) square pieces of parchment paper. Fold squares in half, then open flat. Arrange shrimp on paper. Spoon pineapple chunks in the middle of each piece of parchment. Spoon 1/4 cup mushrooms mixture over pineapples along with 1 teaspoon pineapple juice mixture.
Fold paper and secure edges to form a package. Bake at 400 degrees F for 10 minutes, or until golden and puffy. Cut open and serve right away.