Peach and Blueberry Crisp

unbleached all purpose flour

packed dark brown sugar

sugar

salt

cinnamon

chopped toasted pecans, almonds or walnuts ((I used pecans))

chilled unsalted butter cut into 1-inch pieces

large ripe peaches, pitted and sliced into 12-14 pieces each

ripe blueberries

packed dark brown sugar

minute tapioca

Several drops aged balsamic vinegar or fresh lemon juice ((I used a honey orange balsamic))

Vanilla ice cream or crème fraîche for serving