granny smith apples, peeled and sliced (firm tart baking apples)
Preheat oven to 375 °F (180 °C).
Mix flour, salt and sugar. Add 2 oz. butter and carefully work together to form a rough dough ball. Add the remaining butter and mix well, about 5 minutes, leaving some of the butter looking under mixed and "chunky" looking.
Add the water until the dough just comes together, about 2-3 minutes. Wrap in plastic and let rest about 15 minutes.
Toss the apples, huckleberries and sugar together.
Roll out dough very thin, about 1/8 inch thick. Place dough on 9 inch tart pan; edges of dough will overlap the sides, about 1 1/2".
Place apples on dough. Fold dough over fruit. Brush melted butter over edges.
Bake in oven until very dark and crispy, about 35 to 40 minutes. Slide the cooked tart on a rack to cool. Serve with ice cream.