1. In a small bowl, stir together the gelatin and the 8 tablespoons of cold water. Set aside to allow the gelatin to bloom.
2. Line a baking sheet (half-sheet size) with parchment paper and sprinkle powdered sugar all over the parchment. This will prevent sticking. Set aside.
3. Using a food processor or blender, puree the thawed strawberries until smooth. This is the heart of your marshmallow flavor, so make sure to blend well.
4. In a medium saucepan, combine the strawberry puree, granulated sugar, and salt. Stir together over medium heat until the sugar is completely dissolved.
5. Add the bloomed gelatin to the sugar mixture. Raise the heat to medium-high and whisk together until the gelatin is fully incorporated and the mixture comes to a gentle boil.
6. Once boiling, remove from heat and add the vanilla. Carefully pour the hot strawberry syrup into the bowl of an electric mixer fitted with the whisk attachment.
7. Gradually increase the mixer speed to high, taking care to avoid splashing yourself with the hot syrup. Allow the mixture to whisk on high for about 15 minutes, until it has doubled in volume and is smooth and shiny.
8. Immediately pour the mixture into the prepared pan, using a spatula to spread the marshmallow fluff into an even layer. Allow it to sit for at least several hours, preferably overnight, to set. The marshmallows are ready to cut when they are no longer sticky to the touch.
9. When you're ready to cut, sprinkle more powdered sugar on top of the marshmallows. Use a heart-shaped cookie cutter or a pizza cutter to cut them into your desired shapes. Use a metal spatula to lift them off the sheet carefully to retain their shape.
10. For the chocolate coating, melt together the chocolate chips and vegetable shortening. You can do this on a double boiler or in the microwave in 15 to 20-second increments, stirring in between until the chocolate is completely melted and viscous.
11. Dip the marshmallows in the melted chocolate and lay them on a clean piece of parchment paper. Top with sprinkles if desired. Refrigerate for at least an hour to allow the chocolate to set up.
