1. Make filling: Cook filling ingredients in a medium pan over low heat, stirring, until butter has melted. Raise heat to medium-high; cook for 5 minutes, stirring, until apples release juice. Let cool.
2. Make crust: Beat cream cheese and butter until combined. Add flour and salt; mix just until dough forms. Divide into 24 1-inch balls. Press 1 ball in each cup of a miniature muffin tin so dough covers sides and bottom evenly. (If dough is very soft, chill for 10 minutes before dividing and shaping.)
3. Make topping: Mix flour, both sugars, cinnamon and salt. Rub in butter with your fingers until mixture resembles coarse crumbs. Toss in walnuts.
4. Preheat oven to 350ºF. Divide filling among muffin cups, leaving juices behind. Gently press topping over apples. Bake until golden, 30 to 40 minutes. Let cool on a wire rack for 15 minutes. Using a small metal spatula, remove pies and place on rack to cool completely.