In a medium bowl, combine flour, sugar, and salt. Add cubed butter and with a pastry blender, fork, or your fingertips, work the butter into the flour mixture until it resembles coarse meal.
Add heavy whipping cream and 2 tablespoons of ice water, then mix everything together using your hands until dough comes together. If the dough is dry, add another tablespoon of ice water or more as needed. Form dough into two equal discs and wrap each in plastic wrap. Refrigerate for one hour or up to two days.
Place a piece of large plastic wrap on your work surface. Line a baking sheet with parchment paper; set aside until ready to use. Remove one dough disc from the refrigerator, unwrap, and place onto plastic wrap. Place a second large piece of plastic wrap over dough and roll into a 10" x 13" rectangle. Trim the rectangle down to a 9" x 12" rectangle and then cut into 9 equal pieces, each 3" x 4".
Gently transfer the pop tart shells to the lined baking sheet. Place baking sheet in the freezer and repeat the above step with the second disc of dough.
Once all of the dough is cut, heat oven to 350ºF. Remove pastries from the refrigerator. Brush the edges of 9 pop tarts with heavy whipping cream (this will help the dough stick together). Place a scant tablespoon of lemon curd in the middle of each pop tart. Lightly spread evenly but not to the edges.
Place the remaining 9 pastries over the filling and press down slightly around the edges with your fingertips. Using a fork, create indentations around the edges (this also helps seal the pop tarts so the filling doesn't spill out). Brush heavy whipping cream over the tops of the pop tarts and then using a fork, create 4 to 5 air holes on the tops.
Bake 30 minutes, or until light golden brown, and let cool completely.
For the icing, whisk together powdered sugar, blueberries, and heavy whipping cream until smooth. Heat icing in the microwave for about 15 seconds to soften. Spread icing over pop tarts and garnish with additional blueberries. Serve.