Combine flour and salt in a medium bowl; cut in butter and shortening with a pastry blender until mixture is crumbly. Sprinkle milk, 1 tablespoon at a time, evenly over surface; stir with a fork until dry ingredients are moistened.
Shape into a ball; roll pastry to 1/8-inch thickness on a lightly floured surface. Cut dough into 6 (5-inch) circles; fit into 6 (4-inch) tart pans with removable bottoms. Prick bottoms of tart shells with a fork; place on a baking sheet. Bake at 450º for 10 minutes or until golden. Cool completely.
Sauté apples in melted butter in a large nonstick skillet 5 minutes; gently stir in brown sugar. Cook, stirring often, over medium-high heat 4 to 5 minutes or until sugar is syrupy and apples are tender yet retain their shape. Remove from heat, and let cool.
Spoon apple mixture into prepared tart shells, and sprinkle with huckleberries. Serve immediately.