Preheat the oven to 450°. Line a half sheet pan with a silpat or parchment paper. Set aside.
Line a work surface with plastic wrap. Set the pie pastry in the center and lay another layer of plastic wrap over the pastry. Use a rolling pin to roll out the pie pastry to about 10"-11" round. Remove one layer of plastic and turn the pie pastry out onto the silpat. Remove the other layer of plastic wrap and discard.
Wash the berries with cool water. If using strawberries, remove the stems and cut into quarters or eighths depending on how large they are. Combine the berries in a large bowl and set aside.
In a small bowl, combine the sugar and Instant ClearJel until well mixed.
Sprinkle the sugar mixture over the berries and carefully fold it into the berries until the fruit is well coated.
Pile the berries into the center of the pie crust, leaving about 1 1/2" - 2" border. Fold the edges of the pastry over the berries, overlapping and lightly pinching at the edges.
Brush the pastry with creamand sprinkle the entire tart with sparkling sugar. Bake for 20-25 minutes or until the pastry is golden and the center is bubbly. Tart may leak, but that's ok,
Let the tart rest for 20 minutes or to room temperature then transfer to a serving platter to slice. Serve with ice cream, whipped cream or powdered sugar.