Roll out half of the hamantashen dough to a 1/8" thick circle to fit in a 9" pie pan and transfer to the pan. If the dough breaks at all during transfer, just press it back together.
Top the pie dough with the jam filling.
Coat blueberries in cornstarch and pour over jam.
Cover edge of the crust with foil or a pie guard.
Bake for 40 minutes. The blueberries should be nice and bubbly and not super liquidy.
While the pie is baking, make hamantashen with the second half of the dough and the hamantashen jam filling. There are detailed instructions for shaping hamantashen in my hamantashen recipe post. I used a 2" circle cookie cutter.
Remove the pie from the oven and cover the whole top with unbaked hamantashen - a little overlap is OK, but aim for a single layer.
Bake for another 15-20 minutes with the pie guard still on. Check on the pie frequently to ensure that the hamantashen don't burn. They should be a nice golden brown.