Place the blueberries in a large bowl. Sprinkle the sugar and lemon juice and stir. Add the flour and toss around to coat the berries. Set aside.
Pour the heavy cream and stir the mixture with a fork until a soft, slightly wet dough forms. If the dough is too dry and stiff, add up to 1/4 cup of heavy cream.
Pour and level the blueberries in a 9x13 inch glass baking dish or a 10-inch pie plate or any glass baking dish of comparable size. Arrange the bits of butter over the berries. Scoop the dough all over the tops of the blueberries. Set the dish on a baking sheet lined with foil or parchment paper and bake for 12-14 minutes or until the pastry is golden and the fruit filling is bubbly.
Cobbler dough recipe adapted from Baking with Julia, Johnnycake Cobbler Recipe